// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * INET         An implementation of the TCP/IP protocol suite for the LINUX
 *              operating system.  INET is implemented using the  BSD Socket
 *              interface as the means of communication with the user level.
 *
 *              PF_INET protocol family socket handler.
 *
 * Authors:     Ross Biro
 *              Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
 *              Florian La Roche, <flla@stud.uni-sb.de>
 *              Alan Cox, <A.Cox@swansea.ac.uk>
 *
 * Changes (see also sock.c)
 *
 *              piggy,
 *              Karl Knutson    :       Socket protocol table
 *              A.N.Kuznetsov   :       Socket death error in accept().
 *              John Richardson :       Fix non blocking error in connect()
 *                                      so sockets that fail to connect
 *                                      don't return -EINPROGRESS.
 *              Alan Cox        :       Asynchronous I/O support
 *              Alan Cox        :       Keep correct socket pointer on sock
 *                                      structures
 *                                      when accept() ed
 *              Alan Cox        :       Semantics of SO_LINGER aren't state
 *                                      moved to close when you look carefully.
 *                                      With this fixed and the accept bug fixed
 *                                      some RPC stuff seems happier.
 *              Niibe Yutaka    :       4.4BSD style write async I/O
 *              Alan Cox,
 *              Tony Gale       :       Fixed reuse semantics.
 *              Alan Cox        :       bind() shouldn't abort existing but dead
 *                                      sockets. Stops FTP netin:.. I hope.
 *              Alan Cox        :       bind() works correctly for RAW sockets.
 *                                      Note that FreeBSD at least was broken
 *                                      in this respect so be careful with
 *                                      compatibility tests...
 *              Alan Cox        :       routing cache support
 *              Alan Cox        :       memzero the socket structure for
 *                                      compactness.
 *              Matt Day        :       nonblock connect error handler
 *              Alan Cox        :       Allow large numbers of pending sockets
 *                                      (eg for big web sites), but only if
 *                                      specifically application requested.
 *              Alan Cox        :       New buffering throughout IP. Used
 *                                      dumbly.
 *              Alan Cox        :       New buffering now used smartly.
 *              Alan Cox        :       BSD rather than common sense
 *                                      interpretation of listen.
 *              Germano Caronni :       Assorted small races.
 *              Alan Cox        :       sendmsg/recvmsg basic support.
 *              Alan Cox        :       Only sendmsg/recvmsg now supported.
 *              Alan Cox        :       Locked down bind (see security list).
 *              Alan Cox        :       Loosened bind a little.
 *              Mike McLagan    :       ADD/DEL DLCI Ioctls
 *      Willy Konynenberg       :       Transparent proxying support.
 *              David S. Miller :       New socket lookup architecture.
 *                                      Some other random speedups.
 *              Cyrus Durgin    :       Cleaned up file for kmod hacks.
 *              Andi Kleen      :       Fix inet_stream_connect TCP race.
 */

#define pr_fmt(fmt) "IPv4: " fmt

#include <linux/err.h>
#include <linux/errno.h>
#include <linux/types.h>
#include <linux/socket.h>
#include <linux/in.h>
#include <linux/kernel.h>
#include <linux/kmod.h>
#include <linux/sched.h>
#include <linux/timer.h>
#include <linux/string.h>
#include <linux/sockios.h>
#include <linux/net.h>
#include <linux/capability.h>
#include <linux/fcntl.h>
#include <linux/mm.h>
#include <linux/interrupt.h>
#include <linux/stat.h>
#include <linux/init.h>
#include <linux/poll.h>
#include <linux/netfilter_ipv4.h>
#include <linux/random.h>
#include <linux/slab.h>

#include <linux/uaccess.h>

#include <linux/inet.h>
#include <linux/igmp.h>
#include <linux/inetdevice.h>
#include <linux/netdevice.h>
#include <net/checksum.h>
#include <net/ip.h>
#include <net/protocol.h>
#include <net/arp.h>
#include <net/route.h>
#include <net/ip_fib.h>
#include <net/inet_connection_sock.h>
#include <net/tcp.h>
#include <net/udp.h>
#include <net/udplite.h>
#include <net/ping.h>
#include <linux/skbuff.h>
#include <net/sock.h>
#include <net/raw.h>
#include <net/icmp.h>
#include <net/inet_common.h>
#include <net/ip_tunnels.h>
#include <net/xfrm.h>
#include <net/net_namespace.h>
#include <net/secure_seq.h>
#ifdef CONFIG_IP_MROUTE
#include <linux/mroute.h>
#endif
#include <net/l3mdev.h>
#include <net/compat.h>

#include <trace/events/sock.h>

/* The inetsw table contains everything that inet_create needs to
 * build a new socket.
 */
static struct list_head inetsw[SOCK_MAX];
static DEFINE_SPINLOCK(inetsw_lock);

/* New destruction routine */

void inet_sock_destruct(struct sock *sk)
{
        struct inet_sock *inet = inet_sk(sk);

        __skb_queue_purge(&sk->sk_receive_queue);
        if (sk->sk_rx_skb_cache) {
                __kfree_skb(sk->sk_rx_skb_cache);
                sk->sk_rx_skb_cache = NULL;
        }
        __skb_queue_purge(&sk->sk_error_queue);

        sk_mem_reclaim(sk);

        if (sk->sk_type == SOCK_STREAM && sk->sk_state != TCP_CLOSE) {
                pr_err("Attempt to release TCP socket in state %d %p\n",
                       sk->sk_state, sk);
                return;
        }
        if (!sock_flag(sk, SOCK_DEAD)) {
                pr_err("Attempt to release alive inet socket %p\n", sk);
                return;
        }

        WARN_ON(atomic_read(&sk->sk_rmem_alloc));
        WARN_ON(refcount_read(&sk->sk_wmem_alloc));
        WARN_ON(sk->sk_wmem_queued);
        WARN_ON(sk->sk_forward_alloc);

        kfree(rcu_dereference_protected(inet->inet_opt, 1));
        dst_release(rcu_dereference_protected(sk->sk_dst_cache, 1));
        dst_release(sk->sk_rx_dst);
        sk_refcnt_debug_dec(sk);
}
EXPORT_SYMBOL(inet_sock_destruct);

/*
 *      The routines beyond this point handle the behaviour of an AF_INET
 *      socket object. Mostly it punts to the subprotocols of IP to do
 *      the work.
 */

/*
 *      Automatically bind an unbound socket.
 */

static int inet_autobind(struct sock *sk)
{
        struct inet_sock *inet;
        /* We may need to bind the socket. */
        lock_sock(sk);
        inet = inet_sk(sk);
        if (!inet->inet_num) {
                if (sk->sk_prot->get_port(sk, 0)) {
                        release_sock(sk);
                        return -EAGAIN;
                }
                inet->inet_sport = htons(inet->inet_num);
        }
        release_sock(sk);
        return 0;
}

/*
 *      Move a socket into listening state.
 */
int inet_listen(struct socket *sock, int backlog)
{
        struct sock *sk = sock->sk;
        unsigned char old_state;
        int err, tcp_fastopen;

        lock_sock(sk);

        err = -EINVAL;
        if (sock->state != SS_UNCONNECTED || sock->type != SOCK_STREAM)
                goto out;

        old_state = sk->sk_state;
        if (!((1 << old_state) & (TCPF_CLOSE | TCPF_LISTEN)))
                goto out;

        WRITE_ONCE(sk->sk_max_ack_backlog, backlog);
        /* Really, if the socket is already in listen state
         * we can only allow the backlog to be adjusted.
         */
        if (old_state != TCP_LISTEN) {
                /* Enable TFO w/o requiring TCP_FASTOPEN socket option.
                 * Note that only TCP sockets (SOCK_STREAM) will reach here.
                 * Also fastopen backlog may already been set via the option
                 * because the socket was in TCP_LISTEN state previously but
                 * was shutdown() rather than close().
                 */
                tcp_fastopen = sock_net(sk)->ipv4.sysctl_tcp_fastopen;
                if ((tcp_fastopen & TFO_SERVER_WO_SOCKOPT1) &&
                    (tcp_fastopen & TFO_SERVER_ENABLE) &&
                    !inet_csk(sk)->icsk_accept_queue.fastopenq.max_qlen) {
                        fastopen_queue_tune(sk, backlog);
                        tcp_fastopen_init_key_once(sock_net(sk));
                }

                err = inet_csk_listen_start(sk, backlog);
                if (err)
                        goto out;
                tcp_call_bpf(sk, BPF_SOCK_OPS_TCP_LISTEN_CB, 0, NULL);
        }
        err = 0;

out:
        release_sock(sk);
        return err;
}
EXPORT_SYMBOL(inet_listen);

/*
 *      Create an inet socket.
 */

static int inet_create(struct net *net, struct socket *sock, int protocol,
                       int kern)
{
        struct sock *sk;
        struct inet_protosw *answer;
        struct inet_sock *inet;
        struct proto *answer_prot;
        unsigned char answer_flags;
        int try_loading_module = 0;
        int err;

        if (protocol < 0 || protocol >= IPPROTO_MAX)
                return -EINVAL;

        sock->state = SS_UNCONNECTED;

        /* Look for the requested type/protocol pair. */
lookup_protocol:
        err = -ESOCKTNOSUPPORT;
        rcu_read_lock();
        list_for_each_entry_rcu(answer, &inetsw[sock->type], list) {

                err = 0;
                /* Check the non-wild match. */
                if (protocol == answer->protocol) {
                        if (protocol != IPPROTO_IP)
                                break;
                } else {
                        /* Check for the two wild cases. */
                        if (IPPROTO_IP == protocol) {
                                protocol = answer->protocol;
                                break;
                        }
                        if (IPPROTO_IP == answer->protocol)
                                break;
                }
                err = -EPROTONOSUPPORT;
        }

        if (unlikely(err)) {
                if (try_loading_module < 2) {
                        rcu_read_unlock();
                        /*
                         * Be more specific, e.g. net-pf-2-proto-132-type-1
                         * (net-pf-PF_INET-proto-IPPROTO_SCTP-type-SOCK_STREAM)
                         */
                        if (++try_loading_module == 1)
                                request_module("net-pf-%d-proto-%d-type-%d",
                                               PF_INET, protocol, sock->type);
                        /*
                         * Fall back to generic, e.g. net-pf-2-proto-132
                         * (net-pf-PF_INET-proto-IPPROTO_SCTP)
                         */
                        else
                                request_module("net-pf-%d-proto-%d",
                                               PF_INET, protocol);
                        goto lookup_protocol;
                } else
                        goto out_rcu_unlock;
        }

        err = -EPERM;
        if (sock->type == SOCK_RAW && !kern &&
            !ns_capable(net->user_ns, CAP_NET_RAW))
                goto out_rcu_unlock;

        sock->ops = answer->ops;
        answer_prot = answer->prot;
        answer_flags = answer->flags;
        rcu_read_unlock();

        WARN_ON(!answer_prot->slab);

        err = -ENOBUFS;
        sk = sk_alloc(net, PF_INET, GFP_KERNEL, answer_prot, kern);
        if (!sk)
                goto out;

        err = 0;
        if (INET_PROTOSW_REUSE & answer_flags)
                sk->sk_reuse = SK_CAN_REUSE;

        inet = inet_sk(sk);
        inet->is_icsk = (INET_PROTOSW_ICSK & answer_flags) != 0;

        inet->nodefrag = 0;

        if (SOCK_RAW == sock->type) {
                inet->inet_num = protocol;
                if (IPPROTO_RAW == protocol)
                        inet->hdrincl = 1;
        }

        if (net->ipv4.sysctl_ip_no_pmtu_disc)
                inet->pmtudisc = IP_PMTUDISC_DONT;
        else
                inet->pmtudisc = IP_PMTUDISC_WANT;

        inet->inet_id = 0;

        sock_init_data(sock, sk);

        sk->sk_destruct    = inet_sock_destruct;
        sk->sk_protocol    = protocol;
        sk->sk_backlog_rcv = sk->sk_prot->backlog_rcv;

        inet->uc_ttl    = -1;
        inet->mc_loop   = 1;
        inet->mc_ttl    = 1;
        inet->mc_all    = 1;
        inet->mc_index  = 0;
        inet->mc_list   = NULL;
        inet->rcv_tos   = 0;

        sk_refcnt_debug_inc(sk);

        if (inet->inet_num) {
                /* It assumes that any protocol which allows
                 * the user to assign a number at socket
                 * creation time automatically
                 * shares.
                 */
                inet->inet_sport = htons(inet->inet_num);
                /* Add to protocol hash chains. */
                err = sk->sk_prot->hash(sk);
                if (err) {
                        sk_common_release(sk);
                        goto out;
                }
        }

        if (sk->sk_prot->init) {
                err = sk->sk_prot->init(sk);
                if (err) {
                        sk_common_release(sk);
                        goto out;
                }
        }

        if (!kern) {
                err = BPF_CGROUP_RUN_PROG_INET_SOCK(sk);
                if (err) {
                        sk_common_release(sk);
                        goto out;
                }
        }
out:
        return err;
out_rcu_unlock:
        rcu_read_unlock();
        goto out;
}


/*
 *      The peer socket should always be NULL (or else). When we call this
 *      function we are destroying the object and from then on nobody
 *      should refer to it.
 */
int inet_release(struct socket *sock)
{
        struct sock *sk = sock->sk;

        if (sk) {
                long timeout;

                if (!sk->sk_kern_sock)
                        BPF_CGROUP_RUN_PROG_INET_SOCK_RELEASE(sk);

                /* Applications forget to leave groups before exiting */
                ip_mc_drop_socket(sk);

                /* If linger is set, we don't return until the close
                 * is complete.  Otherwise we return immediately. The
                 * actually closing is done the same either way.
                 *
                 * If the close is due to the process exiting, we never
                 * linger..
                 */
                timeout = 0;
                if (sock_flag(sk, SOCK_LINGER) &&
                    !(current->flags & PF_EXITING))
                        timeout = sk->sk_lingertime;
                sk->sk_prot->close(sk, timeout);
                sock->sk = NULL;
        }
        return 0;
}
EXPORT_SYMBOL(inet_release);

int inet_bind(struct socket *sock, struct sockaddr *uaddr, int addr_len)
{
        struct sock *sk = sock->sk;
        u32 flags = BIND_WITH_LOCK;
        int err;

        /* If the socket has its own bind function then use it. (RAW) */
        if (sk->sk_prot->bind) {
                return sk->sk_prot->bind(sk, uaddr, addr_len);
        }
        if (addr_len < sizeof(struct sockaddr_in))
                return -EINVAL;

        /* BPF prog is run before any checks are done so that if the prog
         * changes context in a wrong way it will be caught.
         */
        err = BPF_CGROUP_RUN_PROG_INET_BIND_LOCK(sk, uaddr,
                                                 BPF_CGROUP_INET4_BIND, &flags);
        if (err)
                return err;

        return __inet_bind(sk, uaddr, addr_len, flags);
}
EXPORT_SYMBOL(inet_bind);

int __inet_bind(struct sock *sk, struct sockaddr *uaddr, int addr_len,
                u32 flags)
{
        struct sockaddr_in *addr = (struct sockaddr_in *)uaddr;
        struct inet_sock *inet = inet_sk(sk);
        struct net *net = sock_net(sk);
        unsigned short snum;
        int chk_addr_ret;
        u32 tb_id = RT_TABLE_LOCAL;
        int err;

        if (addr->sin_family != AF_INET) {
                /* Compatibility games : accept AF_UNSPEC (mapped to AF_INET)
                 * only if s_addr is INADDR_ANY.
                 */
                err = -EAFNOSUPPORT;
                if (addr->sin_family != AF_UNSPEC ||
                    addr->sin_addr.s_addr != htonl(INADDR_ANY))
                        goto out;
        }

        tb_id = l3mdev_fib_table_by_index(net, sk->sk_bound_dev_if) ? : tb_id;
        chk_addr_ret = inet_addr_type_table(net, addr->sin_addr.s_addr, tb_id);

        /* Not specified by any standard per-se, however it breaks too
         * many applications when removed.  It is unfortunate since
         * allowing applications to make a non-local bind solves
         * several problems with systems using dynamic addressing.
         * (ie. your servers still start up even if your ISDN link
         *  is temporarily down)
         */
        err = -EADDRNOTAVAIL;
        if (!inet_can_nonlocal_bind(net, inet) &&
            addr->sin_addr.s_addr != htonl(INADDR_ANY) &&
            chk_addr_ret != RTN_LOCAL &&
            chk_addr_ret != RTN_MULTICAST &&
            chk_addr_ret != RTN_BROADCAST)
                goto out;

        snum = ntohs(addr->sin_port);
        err = -EACCES;
        if (!(flags & BIND_NO_CAP_NET_BIND_SERVICE) &&
            snum && inet_port_requires_bind_service(net, snum) &&
            !ns_capable(net->user_ns, CAP_NET_BIND_SERVICE))
                goto out;

        /*      We keep a pair of addresses. rcv_saddr is the one
         *      used by hash lookups, and saddr is used for transmit.
         *
         *      In the BSD API these are the same except where it
         *      would be illegal to use them (multicast/broadcast) in
         *      which case the sending device address is used.
         */
        if (flags & BIND_WITH_LOCK)
                lock_sock(sk);

        /* Check these errors (active socket, double bind). */
        err = -EINVAL;
        if (sk->sk_state != TCP_CLOSE || inet->inet_num)
                goto out_release_sock;

        inet->inet_rcv_saddr = inet->inet_saddr = addr->sin_addr.s_addr;
        if (chk_addr_ret == RTN_MULTICAST || chk_addr_ret == RTN_BROADCAST)
                inet->inet_saddr = 0;  /* Use device */

        /* Make sure we are allowed to bind here. */
        if (snum || !(inet->bind_address_no_port ||
                      (flags & BIND_FORCE_ADDRESS_NO_PORT))) {
                if (sk->sk_prot->get_port(sk, snum)) {
                        inet->inet_saddr = inet->inet_rcv_saddr = 0;
                        err = -EADDRINUSE;
                        goto out_release_sock;
                }
                if (!(flags & BIND_FROM_BPF)) {
                        err = BPF_CGROUP_RUN_PROG_INET4_POST_BIND(sk);
                        if (err) {
                                inet->inet_saddr = inet->inet_rcv_saddr = 0;
                                goto out_release_sock;
                        }
                }
        }

        if (inet->inet_rcv_saddr)
                sk->sk_userlocks |= SOCK_BINDADDR_LOCK;
        if (snum)
                sk->sk_userlocks |= SOCK_BINDPORT_LOCK;
        inet->inet_sport = htons(inet->inet_num);
        inet->inet_daddr = 0;
        inet->inet_dport = 0;
        sk_dst_reset(sk);
        err = 0;
out_release_sock:
        if (flags & BIND_WITH_LOCK)
                release_sock(sk);
out:
        return err;
}

int inet_dgram_connect(struct socket *sock, struct sockaddr *uaddr,
                       int addr_len, int flags)
{
        struct sock *sk = sock->sk;
        int err;

        if (addr_len < sizeof(uaddr->sa_family))
                return -EINVAL;
        if (uaddr->sa_family == AF_UNSPEC)
                return sk->sk_prot->disconnect(sk, flags);

        if (BPF_CGROUP_PRE_CONNECT_ENABLED(sk)) {
                err = sk->sk_prot->pre_connect(sk, uaddr, addr_len);
                if (err)
                        return err;
        }

        if (!inet_sk(sk)->inet_num && inet_autobind(sk))
                return -EAGAIN;
        return sk->sk_prot->connect(sk, uaddr, addr_len);
}
EXPORT_SYMBOL(inet_dgram_connect);

static long inet_wait_for_connect(struct sock *sk, long timeo, int writebias)
{
        DEFINE_WAIT_FUNC(wait, woken_wake_function);

        add_wait_queue(sk_sleep(sk), &wait);
        sk->sk_write_pending += writebias;

        /* Basic assumption: if someone sets sk->sk_err, he _must_
         * change state of the socket from TCP_SYN_*.
         * Connect() does not allow to get error notifications
         * without closing the socket.
         */
        while ((1 << sk->sk_state) & (TCPF_SYN_SENT | TCPF_SYN_RECV)) {
                release_sock(sk);
                timeo = wait_woken(&wait, TASK_INTERRUPTIBLE, timeo);
                lock_sock(sk);
                if (signal_pending(current) || !timeo)
                        break;
        }
        remove_wait_queue(sk_sleep(sk), &wait);
        sk->sk_write_pending -= writebias;
        return timeo;
}

/*
 *      Connect to a remote host. There is regrettably still a little
 *      TCP 'magic' in here.
 */
int __inet_stream_connect(struct socket *sock, struct sockaddr *uaddr,
                          int addr_len, int flags, int is_sendmsg)
{
        struct sock *sk = sock->sk;
        int err;
        long timeo;

        /*
         * uaddr can be NULL and addr_len can be 0 if:
         * sk is a TCP fastopen active socket and
         * TCP_FASTOPEN_CONNECT sockopt is set and
         * we already have a valid cookie for this socket.
         * In this case, user can call write() after connect().
         * write() will invoke tcp_sendmsg_fastopen() which calls
         * __inet_stream_connect().
         */
        if (uaddr) {
                if (addr_len < sizeof(uaddr->sa_family))
                        return -EINVAL;

                if (uaddr->sa_family == AF_UNSPEC) {
                        err = sk->sk_prot->disconnect(sk, flags);
                        sock->state = err ? SS_DISCONNECTING : SS_UNCONNECTED;
                        goto out;
                }
        }

        switch (sock->state) {
        default:
                err = -EINVAL;
                goto out;
        case SS_CONNECTED:
                err = -EISCONN;
                goto out;
        case SS_CONNECTING:
                if (inet_sk(sk)->defer_connect)
                        err = is_sendmsg ? -EINPROGRESS : -EISCONN;
                else
                        err = -EALREADY;
                /* Fall out of switch with err, set for this state */
                break;
        case SS_UNCONNECTED:
                err = -EISCONN;
                if (sk->sk_state != TCP_CLOSE)
                        goto out;

                if (BPF_CGROUP_PRE_CONNECT_ENABLED(sk)) {
                        err = sk->sk_prot->pre_connect(sk, uaddr, addr_len);
                        if (err)
                                goto out;
                }

                err = sk->sk_prot->connect(sk, uaddr, addr_len);
                if (err < 0)
                        goto out;

                sock->state = SS_CONNECTING;

                if (!err && inet_sk(sk)->defer_connect)
                        goto out;

                /* Just entered SS_CONNECTING state; the only
                 * difference is that return value in non-blocking
                 * case is EINPROGRESS, rather than EALREADY.
                 */
                err = -EINPROGRESS;
                break;
        }

        timeo = sock_sndtimeo(sk, flags & O_NONBLOCK);

        if ((1 << sk->sk_state) & (TCPF_SYN_SENT | TCPF_SYN_RECV)) {
                int writebias = (sk->sk_protocol == IPPROTO_TCP) &&
                                tcp_sk(sk)->fastopen_req &&
                                tcp_sk(sk)->fastopen_req->data ? 1 : 0;

                /* Error code is set above */
                if (!timeo || !inet_wait_for_connect(sk, timeo, writebias))
                        goto out;

                err = sock_intr_errno(timeo);
                if (signal_pending(current))
                        goto out;
        }

        /* Connection was closed by RST, timeout, ICMP error
         * or another process disconnected us.
         */
        if (sk->sk_state == TCP_CLOSE)
                goto sock_error;

        /* sk->sk_err may be not zero now, if RECVERR was ordered by user
         * and error was received after socket entered established state.
         * Hence, it is handled normally after connect() return successfully.
         */

        sock->state = SS_CONNECTED;
        err = 0;
out:
        return err;

sock_error:
        err = sock_error(sk) ? : -ECONNABORTED;
        sock->state = SS_UNCONNECTED;
        if (sk->sk_prot->disconnect(sk, flags))
                sock->state = SS_DISCONNECTING;
        goto out;
}
EXPORT_SYMBOL(__inet_stream_connect);

int inet_stream_connect(struct socket *sock, struct sockaddr *uaddr,
                        int addr_len, int flags)
{
        int err;

        lock_sock(sock->sk);
        err = __inet_stream_connect(sock, uaddr, addr_len, flags, 0);
        release_sock(sock->sk);
        return err;
}
EXPORT_SYMBOL(inet_stream_connect);

/*
 *      Accept a pending connection. The TCP layer now gives BSD semantics.
 */

int inet_accept(struct socket *sock, struct socket *newsock, int flags,
                bool kern)
{
        struct sock *sk1 = sock->sk;
        int err = -EINVAL;
        struct sock *sk2 = sk1->sk_prot->accept(sk1, flags, &err, kern);

        if (!sk2)
                goto do_err;

        lock_sock(sk2);

        sock_rps_record_flow(sk2);
        WARN_ON(!((1 << sk2->sk_state) &
                  (TCPF_ESTABLISHED | TCPF_SYN_RECV |
                  TCPF_CLOSE_WAIT | TCPF_CLOSE)));

        sock_graft(sk2, newsock);

        newsock->state = SS_CONNECTED;
        err = 0;
        release_sock(sk2);
do_err:
        return err;
}
EXPORT_SYMBOL(inet_accept);

/*
 *      This does both peername and sockname.
 */
int inet_getname(struct socket *sock, struct sockaddr *uaddr,
                 int peer)
{
        struct sock *sk         = sock->sk;
        struct inet_sock *inet  = inet_sk(sk);
        DECLARE_SOCKADDR(struct sockaddr_in *, sin, uaddr);

        sin->sin_family = AF_INET;
        if (peer) {
                if (!inet->inet_dport ||
                    (((1 << sk->sk_state) & (TCPF_CLOSE | TCPF_SYN_SENT)) &&
                     peer == 1))
                        return -ENOTCONN;
                sin->sin_port = inet->inet_dport;
                sin->sin_addr.s_addr = inet->inet_daddr;
                BPF_CGROUP_RUN_SA_PROG_LOCK(sk, (struct sockaddr *)sin,
                                            BPF_CGROUP_INET4_GETPEERNAME,
                                            NULL);
        } else {
                __be32 addr = inet->inet_rcv_saddr;
                if (!addr)
                        addr = inet->inet_saddr;
                sin->sin_port = inet->inet_sport;
                sin->sin_addr.s_addr = addr;
                BPF_CGROUP_RUN_SA_PROG_LOCK(sk, (struct sockaddr *)sin,
                                            BPF_CGROUP_INET4_GETSOCKNAME,
                                            NULL);
        }
        memset(sin->sin_zero, 0, sizeof(sin->sin_zero));
        return sizeof(*sin);
}
EXPORT_SYMBOL(inet_getname);

int inet_send_prepare(struct sock *sk)
{
        sock_rps_record_flow(sk);

        /* We may need to bind the socket. */
        if (!inet_sk(sk)->inet_num && !sk->sk_prot->no_autobind &&
            inet_autobind(sk))
                return -EAGAIN;

        return 0;
}
EXPORT_SYMBOL_GPL(inet_send_prepare);

int inet_sendmsg(struct socket *sock, struct msghdr *msg, size_t size)
{
        struct sock *sk = sock->sk;

        if (unlikely(inet_send_prepare(sk)))
                return -EAGAIN;

        return INDIRECT_CALL_2(sk->sk_prot->sendmsg, tcp_sendmsg, udp_sendmsg,
                               sk, msg, size);
}
EXPORT_SYMBOL(inet_sendmsg);

ssize_t inet_sendpage(struct socket *sock, struct page *page, int offset,
                      size_t size, int flags)
{
        struct sock *sk = sock->sk;

        if (unlikely(inet_send_prepare(sk)))
                return -EAGAIN;

        if (sk->sk_prot->sendpage)
                return sk->sk_prot->sendpage(sk, page, offset, size, flags);
        return sock_no_sendpage(sock, page, offset, size, flags);
}
EXPORT_SYMBOL(inet_sendpage);

INDIRECT_CALLABLE_DECLARE(int udp_recvmsg(struct sock *, struct msghdr *,
                                          size_t, int, int, int *));
int inet_recvmsg(struct socket *sock, struct msghdr *msg, size_t size,
                 int flags)
{
        struct sock *sk = sock->sk;
        int addr_len = 0;
        int err;

        if (likely(!(flags & MSG_ERRQUEUE)))
                sock_rps_record_flow(sk);

        err = INDIRECT_CALL_2(sk->sk_prot->recvmsg, tcp_recvmsg, udp_recvmsg,
                              sk, msg, size, flags & MSG_DONTWAIT,
                              flags & ~MSG_DONTWAIT, &addr_len);
        if (err >= 0)
                msg->msg_namelen = addr_len;
        return err;
}
EXPORT_SYMBOL(inet_recvmsg);

int inet_shutdown(struct socket *sock, int how)
{
        struct sock *sk = sock->sk;
        int err = 0;

        /* This should really check to make sure
         * the socket is a TCP socket. (WHY AC...)
         */
        how++; /* maps 0->1 has the advantage of making bit 1 rcvs and
                       1->2 bit 2 snds.
                       2->3 */
        if ((how & ~SHUTDOWN_MASK) || !how)     /* MAXINT->0 */
                return -EINVAL;

        lock_sock(sk);
        if (sock->state == SS_CONNECTING) {
                if ((1 << sk->sk_state) &
                    (TCPF_SYN_SENT | TCPF_SYN_RECV | TCPF_CLOSE))
                        sock->state = SS_DISCONNECTING;
                else
                        sock->state = SS_CONNECTED;
        }

        switch (sk->sk_state) {
        case TCP_CLOSE:
                err = -ENOTCONN;
                /* Hack to wake up other listeners, who can poll for
                   EPOLLHUP, even on eg. unconnected UDP sockets -- RR */
                fallthrough;
        default:
                sk->sk_shutdown |= how;
                if (sk->sk_prot->shutdown)
                        sk->sk_prot->shutdown(sk, how);
                break;

        /* Remaining two branches are temporary solution for missing
         * close() in multithreaded environment. It is _not_ a good idea,
         * but we have no choice until close() is repaired at VFS level.
         */
        case TCP_LISTEN:
                if (!(how & RCV_SHUTDOWN))
                        break;
                fallthrough;
        case TCP_SYN_SENT:
                err = sk->sk_prot->disconnect(sk, O_NONBLOCK);
                sock->state = err ? SS_DISCONNECTING : SS_UNCONNECTED;
                break;
        }

        /* Wake up anyone sleeping in poll. */
        sk->sk_state_change(sk);
        release_sock(sk);
        return err;
}
EXPORT_SYMBOL(inet_shutdown);

/*
 *      ioctl() calls you can issue on an INET socket. Most of these are
 *      device configuration and stuff and very rarely used. Some ioctls
 *      pass on to the socket itself.
 *
 *      NOTE: I like the idea of a module for the config stuff. ie ifconfig
 *      loads the devconfigure module does its configuring and unloads it.
 *      There's a good 20K of config code hanging around the kernel.
 */

int inet_ioctl(struct socket *sock, unsigned int cmd, unsigned long arg)
{
        struct sock *sk = sock->sk;
        int err = 0;
        struct net *net = sock_net(sk);
        void __user *p = (void __user *)arg;
        struct ifreq ifr;
        struct rtentry rt;

        switch (cmd) {
        case SIOCADDRT:
        case SIOCDELRT:
                if (copy_from_user(&rt, p, sizeof(struct rtentry)))
                        return -EFAULT;
                err = ip_rt_ioctl(net, cmd, &rt);
                break;
        case SIOCRTMSG:
                err = -EINVAL;
                break;
        case SIOCDARP:
        case SIOCGARP:
        case SIOCSARP:
                err = arp_ioctl(net, cmd, (void __user *)arg);
                break;
        case SIOCGIFADDR:
        case SIOCGIFBRDADDR:
        case SIOCGIFNETMASK:
        case SIOCGIFDSTADDR:
        case SIOCGIFPFLAGS:
                if (copy_from_user(&ifr, p, sizeof(struct ifreq)))
                        return -EFAULT;
                err = devinet_ioctl(net, cmd, &ifr);
                if (!err && copy_to_user(p, &ifr, sizeof(struct ifreq)))
                        err = -EFAULT;
                break;

        case SIOCSIFADDR:
        case SIOCSIFBRDADDR:
        case SIOCSIFNETMASK:
        case SIOCSIFDSTADDR:
        case SIOCSIFPFLAGS:
        case SIOCSIFFLAGS:
                if (copy_from_user(&ifr, p, sizeof(struct ifreq)))
                        return -EFAULT;
                err = devinet_ioctl(net, cmd, &ifr);
                break;
        default:
                if (sk->sk_prot->ioctl)
                        err = sk->sk_prot->ioctl(sk, cmd, arg);
                else
                        err = -ENOIOCTLCMD;
                break;
        }
        return err;
}
EXPORT_SYMBOL(inet_ioctl);

#ifdef CONFIG_COMPAT
static int inet_compat_routing_ioctl(struct sock *sk, unsigned int cmd,
                struct compat_rtentry __user *ur)
{
        compat_uptr_t rtdev;
        struct rtentry rt;

        if (copy_from_user(&rt.rt_dst, &ur->rt_dst,
                        3 * sizeof(struct sockaddr)) ||
            get_user(rt.rt_flags, &ur->rt_flags) ||
            get_user(rt.rt_metric, &ur->rt_metric) ||
            get_user(rt.rt_mtu, &ur->rt_mtu) ||
            get_user(rt.rt_window, &ur->rt_window) ||
            get_user(rt.rt_irtt, &ur->rt_irtt) ||
            get_user(rtdev, &ur->rt_dev))
                return -EFAULT;

        rt.rt_dev = compat_ptr(rtdev);
        return ip_rt_ioctl(sock_net(sk), cmd, &rt);
}

static int inet_compat_ioctl(struct socket *sock, unsigned int cmd, unsigned long arg)
{
        void __user *argp = compat_ptr(arg);
        struct sock *sk = sock->sk;

        switch (cmd) {
        case SIOCADDRT:
        case SIOCDELRT:
                return inet_compat_routing_ioctl(sk, cmd, argp);
        default:
                if (!sk->sk_prot->compat_ioctl)
                        return -ENOIOCTLCMD;
                return sk->sk_prot->compat_ioctl(sk, cmd, arg);
        }
}
#endif /* CONFIG_COMPAT */

const struct proto_ops inet_stream_ops = {
        .family            = PF_INET,
        .owner             = THIS_MODULE,
        .release           = inet_release,
        .bind              = inet_bind,
        .connect           = inet_stream_connect,
        .socketpair        = sock_no_socketpair,
        .accept            = inet_accept,
        .getname           = inet_getname,
        .poll              = tcp_poll,
        .ioctl             = inet_ioctl,
        .gettstamp         = sock_gettstamp,
        .listen            = inet_listen,
        .shutdown          = inet_shutdown,
        .setsockopt        = sock_common_setsockopt,
        .getsockopt        = sock_common_getsockopt,
        .sendmsg           = inet_sendmsg,
        .recvmsg           = inet_recvmsg,
#ifdef CONFIG_MMU
        .mmap              = tcp_mmap,
#endif
        .sendpage          = inet_sendpage,
        .splice_read       = tcp_splice_read,
        .read_sock         = tcp_read_sock,
        .sendmsg_locked    = tcp_sendmsg_locked,
        .sendpage_locked   = tcp_sendpage_locked,
        .peek_len          = tcp_peek_len,
#ifdef CONFIG_COMPAT
        .compat_ioctl      = inet_compat_ioctl,
#endif
        .set_rcvlowat      = tcp_set_rcvlowat,
};
EXPORT_SYMBOL(inet_stream_ops);

const struct proto_ops inet_dgram_ops = {
        .family            = PF_INET,
        .owner             = THIS_MODULE,
        .release           = inet_release,
        .bind              = inet_bind,
        .connect           = inet_dgram_connect,
        .socketpair        = sock_no_socketpair,
        .accept            = sock_no_accept,
        .getname           = inet_getname,
        .poll              = udp_poll,
        .ioctl             = inet_ioctl,
        .gettstamp         = sock_gettstamp,
        .listen            = sock_no_listen,
        .shutdown          = inet_shutdown,
        .setsockopt        = sock_common_setsockopt,
        .getsockopt        = sock_common_getsockopt,
        .sendmsg           = inet_sendmsg,
        .recvmsg           = inet_recvmsg,
        .mmap              = sock_no_mmap,
        .sendpage          = inet_sendpage,
        .set_peek_off      = sk_set_peek_off,
#ifdef CONFIG_COMPAT
        .compat_ioctl      = inet_compat_ioctl,
#endif
};
EXPORT_SYMBOL(inet_dgram_ops);

/*
 * For SOCK_RAW sockets; should be the same as inet_dgram_ops but without
 * udp_poll
 */
static const struct proto_ops inet_sockraw_ops = {
        .family            = PF_INET,
        .owner             = THIS_MODULE,
        .release           = inet_release,
        .bind              = inet_bind,
        .connect           = inet_dgram_connect,
        .socketpair        = sock_no_socketpair,
        .accept            = sock_no_accept,
        .getname           = inet_getname,
        .poll              = datagram_poll,
        .ioctl             = inet_ioctl,
        .gettstamp         = sock_gettstamp,
        .listen            = sock_no_listen,
        .shutdown          = inet_shutdown,
        .setsockopt        = sock_common_setsockopt,
        .getsockopt        = sock_common_getsockopt,
        .sendmsg           = inet_sendmsg,
        .recvmsg           = inet_recvmsg,
        .mmap              = sock_no_mmap,
        .sendpage          = inet_sendpage,
#ifdef CONFIG_COMPAT
        .compat_ioctl      = inet_compat_ioctl,
#endif
};

static const struct net_proto_family inet_family_ops = {
        .family = PF_INET,
        .create = inet_create,
        .owner  = THIS_MODULE,
};

/* Upon startup we insert all the elements in inetsw_array[] into
 * the linked list inetsw.
 */
static struct inet_protosw inetsw_array[] =
{
        {
                .type =       SOCK_STREAM,
                .protocol =   IPPROTO_TCP,
                .prot =       &tcp_prot,
                .ops =        &inet_stream_ops,
                .flags =      INET_PROTOSW_PERMANENT |
                              INET_PROTOSW_ICSK,
        },

        {
                .type =       SOCK_DGRAM,
                .protocol =   IPPROTO_UDP,
                .prot =       &udp_prot,
                .ops =        &inet_dgram_ops,
                .flags =      INET_PROTOSW_PERMANENT,
       },

       {
                .type =       SOCK_DGRAM,
                .protocol =   IPPROTO_ICMP,
                .prot =       &ping_prot,
                .ops =        &inet_sockraw_ops,
                .flags =      INET_PROTOSW_REUSE,
       },

       {
               .type =       SOCK_RAW,
               .protocol =   IPPROTO_IP,        /* wild card */
               .prot =       &raw_prot,
               .ops =        &inet_sockraw_ops,
               .flags =      INET_PROTOSW_REUSE,
       }
};

#define INETSW_ARRAY_LEN ARRAY_SIZE(inetsw_array)

void inet_register_protosw(struct inet_protosw *p)
{
        struct list_head *lh;
        struct inet_protosw *answer;
        int protocol = p->protocol;
        struct list_head *last_perm;

        spin_lock_bh(&inetsw_lock);

        if (p->type >= SOCK_MAX)
                goto out_illegal;

        /* If we are trying to override a permanent protocol, bail. */
        last_perm = &inetsw[p->type];
        list_for_each(lh, &inetsw[p->type]) {
                answer = list_entry(lh, struct inet_protosw, list);
                /* Check only the non-wild match. */
                if ((INET_PROTOSW_PERMANENT & answer->flags) == 0)
                        break;
                if (protocol == answer->protocol)
                        goto out_permanent;
                last_perm = lh;
        }

        /* Add the new entry after the last permanent entry if any, so that
         * the new entry does not override a permanent entry when matched with
         * a wild-card protocol. But it is allowed to override any existing
         * non-permanent entry.  This means that when we remove this entry, the
         * system automatically returns to the old behavior.
         */
        list_add_rcu(&p->list, last_perm);
out:
        spin_unlock_bh(&inetsw_lock);

        return;

out_permanent:
        pr_err("Attempt to override permanent protocol %d\n", protocol);
        goto out;

out_illegal:
        pr_err("Ignoring attempt to register invalid socket type %d\n",
               p->type);
        goto out;
}
EXPORT_SYMBOL(inet_register_protosw);

void inet_unregister_protosw(struct inet_protosw *p)
{
        if (INET_PROTOSW_PERMANENT & p->flags) {
                pr_err("Attempt to unregister permanent protocol %d\n",
                       p->protocol);
        } else {
                spin_lock_bh(&inetsw_lock);
                list_del_rcu(&p->list);
                spin_unlock_bh(&inetsw_lock);

                synchronize_net();
        }
}
EXPORT_SYMBOL(inet_unregister_protosw);

static int inet_sk_reselect_saddr(struct sock *sk)
{
        struct inet_sock *inet = inet_sk(sk);
        __be32 old_saddr = inet->inet_saddr;
        __be32 daddr = inet->inet_daddr;
        struct flowi4 *fl4;
        struct rtable *rt;
        __be32 new_saddr;
        struct ip_options_rcu *inet_opt;

        inet_opt = rcu_dereference_protected(inet->inet_opt,
                                             lockdep_sock_is_held(sk));
        if (inet_opt && inet_opt->opt.srr)
                daddr = inet_opt->opt.faddr;

        /* Query new route. */
        fl4 = &inet->cork.fl.u.ip4;
        rt = ip_route_connect(fl4, daddr, 0, RT_CONN_FLAGS(sk),
                              sk->sk_bound_dev_if, sk->sk_protocol,
                              inet->inet_sport, inet->inet_dport, sk);
        if (IS_ERR(rt))
                return PTR_ERR(rt);

        sk_setup_caps(sk, &rt->dst);

        new_saddr = fl4->saddr;

        if (new_saddr == old_saddr)
                return 0;

        if (sock_net(sk)->ipv4.sysctl_ip_dynaddr > 1) {
                pr_info("%s(): shifting inet->saddr from %pI4 to %pI4\n",
                        __func__, &old_saddr, &new_saddr);
        }

        inet->inet_saddr = inet->inet_rcv_saddr = new_saddr;

        /*
         * XXX The only one ugly spot where we need to
         * XXX really change the sockets identity after
         * XXX it has entered the hashes. -DaveM
         *
         * Besides that, it does not check for connection
         * uniqueness. Wait for troubles.
         */
        return __sk_prot_rehash(sk);
}

int inet_sk_rebuild_header(struct sock *sk)
{
        struct inet_sock *inet = inet_sk(sk);
        struct rtable *rt = (struct rtable *)__sk_dst_check(sk, 0);
        __be32 daddr;
        struct ip_options_rcu *inet_opt;
        struct flowi4 *fl4;
        int err;

        /* Route is OK, nothing to do. */
        if (rt)
                return 0;

        /* Reroute. */
        rcu_read_lock();
        inet_opt = rcu_dereference(inet->inet_opt);
        daddr = inet->inet_daddr;
        if (inet_opt && inet_opt->opt.srr)
                daddr = inet_opt->opt.faddr;
        rcu_read_unlock();
        fl4 = &inet->cork.fl.u.ip4;
        rt = ip_route_output_ports(sock_net(sk), fl4, sk, daddr, inet->inet_saddr,
                                   inet->inet_dport, inet->inet_sport,
                                   sk->sk_protocol, RT_CONN_FLAGS(sk),
                                   sk->sk_bound_dev_if);
        if (!IS_ERR(rt)) {
                err = 0;
                sk_setup_caps(sk, &rt->dst);
        } else {
                err = PTR_ERR(rt);

                /* Routing failed... */
                sk->sk_route_caps = 0;
                /*
                 * Other protocols have to map its equivalent state to TCP_SYN_SENT.
                 * DCCP maps its DCCP_REQUESTING state to TCP_SYN_SENT. -acme
                 */
                if (!sock_net(sk)->ipv4.sysctl_ip_dynaddr ||
                    sk->sk_state != TCP_SYN_SENT ||
                    (sk->sk_userlocks & SOCK_BINDADDR_LOCK) ||
                    (err = inet_sk_reselect_saddr(sk)) != 0)
                        sk->sk_err_soft = -err;
        }

        return err;
}
EXPORT_SYMBOL(inet_sk_rebuild_header);

void inet_sk_set_state(struct sock *sk, int state)
{
        trace_inet_sock_set_state(sk, sk->sk_state, state);
        sk->sk_state = state;
}
EXPORT_SYMBOL(inet_sk_set_state);

void inet_sk_state_store(struct sock *sk, int newstate)
{
        trace_inet_sock_set_state(sk, sk->sk_state, newstate);
        smp_store_release(&sk->sk_state, newstate);
}

struct sk_buff *inet_gso_segment(struct sk_buff *skb,
                                 netdev_features_t features)
{
        bool udpfrag = false, fixedid = false, gso_partial, encap;
        struct sk_buff *segs = ERR_PTR(-EINVAL);
        const struct net_offload *ops;
        unsigned int offset = 0;
        struct iphdr *iph;
        int proto, tot_len;
        int nhoff;
        int ihl;
        int id;

        skb_reset_network_header(skb);
        nhoff = skb_network_header(skb) - skb_mac_header(skb);
        if (unlikely(!pskb_may_pull(skb, sizeof(*iph))))
                goto out;

        iph = ip_hdr(skb);
        ihl = iph->ihl * 4;
        if (ihl < sizeof(*iph))
                goto out;

        id = ntohs(iph->id);
        proto = iph->protocol;

        /* Warning: after this point, iph might be no longer valid */
        if (unlikely(!pskb_may_pull(skb, ihl)))
                goto out;
        __skb_pull(skb, ihl);

        encap = SKB_GSO_CB(skb)->encap_level > 0;
        if (encap)
                features &= skb->dev->hw_enc_features;
        SKB_GSO_CB(skb)->encap_level += ihl;

        skb_reset_transport_header(skb);

        segs = ERR_PTR(-EPROTONOSUPPORT);

        if (!skb->encapsulation || encap) {
                udpfrag = !!(skb_shinfo(skb)->gso_type & SKB_GSO_UDP);
                fixedid = !!(skb_shinfo(skb)->gso_type & SKB_GSO_TCP_FIXEDID);

                /* fixed ID is invalid if DF bit is not set */
                if (fixedid && !(ip_hdr(skb)->frag_off & htons(IP_DF)))
                        goto out;
        }

        ops = rcu_dereference(inet_offloads[proto]);
        if (likely(ops && ops->callbacks.gso_segment))
                segs = ops->callbacks.gso_segment(skb, features);

        if (IS_ERR_OR_NULL(segs))
                goto out;

        gso_partial = !!(skb_shinfo(segs)->gso_type & SKB_GSO_PARTIAL);

        skb = segs;
        do {
                iph = (struct iphdr *)(skb_mac_header(skb) + nhoff);
                if (udpfrag) {
                        iph->frag_off = htons(offset >> 3);
                        if (skb->next)
                                iph->frag_off |= htons(IP_MF);
                        offset += skb->len - nhoff - ihl;
                        tot_len = skb->len - nhoff;
                } else if (skb_is_gso(skb)) {
                        if (!fixedid) {
                                iph->id = htons(id);
                                id += skb_shinfo(skb)->gso_segs;
                        }

                        if (gso_partial)
                                tot_len = skb_shinfo(skb)->gso_size +
                                          SKB_GSO_CB(skb)->data_offset +
                                          skb->head - (unsigned char *)iph;
                        else
                                tot_len = skb->len - nhoff;
                } else {
                        if (!fixedid)
                                iph->id = htons(id++);
                        tot_len = skb->len - nhoff;
                }
                iph->tot_len = htons(tot_len);
                ip_send_check(iph);
                if (encap)
                        skb_reset_inner_headers(skb);
                skb->network_header = (u8 *)iph - skb->head;
                skb_reset_mac_len(skb);
        } while ((skb = skb->next));

out:
        return segs;
}

static struct sk_buff *ipip_gso_segment(struct sk_buff *skb,
                                        netdev_features_t features)
{
        if (!(skb_shinfo(skb)->gso_type & SKB_GSO_IPXIP4))
                return ERR_PTR(-EINVAL);

        return inet_gso_segment(skb, features);
}

struct sk_buff *inet_gro_receive(struct list_head *head, struct sk_buff *skb)
{
        const struct net_offload *ops;
        struct sk_buff *pp = NULL;
        const struct iphdr *iph;
        struct sk_buff *p;
        unsigned int hlen;
        unsigned int off;
        unsigned int id;
        int flush = 1;
        int proto;

        off = skb_gro_offset(skb);
        hlen = off + sizeof(*iph);
        iph = skb_gro_header_fast(skb, off);
        if (skb_gro_header_hard(skb, hlen)) {
                iph = skb_gro_header_slow(skb, hlen, off);
                if (unlikely(!iph))
                        goto out;
        }

        proto = iph->protocol;

        rcu_read_lock();
        ops = rcu_dereference(inet_offloads[proto]);
        if (!ops || !ops->callbacks.gro_receive)
                goto out_unlock;

        if (*(u8 *)iph != 0x45)
                goto out_unlock;

        if (ip_is_fragment(iph))
                goto out_unlock;

        if (unlikely(ip_fast_csum((u8 *)iph, 5)))
                goto out_unlock;

        id = ntohl(*(__be32 *)&iph->id);
        flush = (u16)((ntohl(*(__be32 *)iph) ^ skb_gro_len(skb)) | (id & ~IP_DF));
        id >>= 16;

        list_for_each_entry(p, head, list) {
                struct iphdr *iph2;
                u16 flush_id;

                if (!NAPI_GRO_CB(p)->same_flow)
                        continue;

                iph2 = (struct iphdr *)(p->data + off);
                /* The above works because, with the exception of the top
                 * (inner most) layer, we only aggregate pkts with the same
                 * hdr length so all the hdrs we'll need to verify will start
                 * at the same offset.
                 */
                if ((iph->protocol ^ iph2->protocol) |
                    ((__force u32)iph->saddr ^ (__force u32)iph2->saddr) |
                    ((__force u32)iph->daddr ^ (__force u32)iph2->daddr)) {
                        NAPI_GRO_CB(p)->same_flow = 0;
                        continue;
                }

                /* All fields must match except length and checksum. */
                NAPI_GRO_CB(p)->flush |=
                        (iph->ttl ^ iph2->ttl) |
                        (iph->tos ^ iph2->tos) |
                        ((iph->frag_off ^ iph2->frag_off) & htons(IP_DF));

                NAPI_GRO_CB(p)->flush |= flush;

                /* We need to store of the IP ID check to be included later
                 * when we can verify that this packet does in fact belong
                 * to a given flow.
                 */
                flush_id = (u16)(id - ntohs(iph2->id));

                /* This bit of code makes it much easier for us to identify
                 * the cases where we are doing atomic vs non-atomic IP ID
                 * checks.  Specifically an atomic check can return IP ID
                 * values 0 - 0xFFFF, while a non-atomic check can only
                 * return 0 or 0xFFFF.
                 */
                if (!NAPI_GRO_CB(p)->is_atomic ||
                    !(iph->frag_off & htons(IP_DF))) {
                        flush_id ^= NAPI_GRO_CB(p)->count;
                        flush_id = flush_id ? 0xFFFF : 0;
                }

                /* If the previous IP ID value was based on an atomic
                 * datagram we can overwrite the value and ignore it.
                 */
                if (NAPI_GRO_CB(skb)->is_atomic)
                        NAPI_GRO_CB(p)->flush_id = flush_id;
                else
                        NAPI_GRO_CB(p)->flush_id |= flush_id;
        }

        NAPI_GRO_CB(skb)->is_atomic = !!(iph->frag_off & htons(IP_DF));
        NAPI_GRO_CB(skb)->flush |= flush;
        skb_set_network_header(skb, off);
        /* The above will be needed by the transport layer if there is one
         * immediately following this IP hdr.
         */

        /* Note : No need to call skb_gro_postpull_rcsum() here,
         * as we already checked checksum over ipv4 header was 0
         */
        skb_gro_pull(skb, sizeof(*iph));
        skb_set_transport_header(skb, skb_gro_offset(skb));

        pp = indirect_call_gro_receive(tcp4_gro_receive, udp4_gro_receive,
                                       ops->callbacks.gro_receive, head, skb);

out_unlock:
        rcu_read_unlock();

out:
        skb_gro_flush_final(skb, pp, flush);

        return pp;
}

static struct sk_buff *ipip_gro_receive(struct list_head *head,
                                        struct sk_buff *skb)
{
        if (NAPI_GRO_CB(skb)->encap_mark) {
                NAPI_GRO_CB(skb)->flush = 1;
                return NULL;
        }

        NAPI_GRO_CB(skb)->encap_mark = 1;

        return inet_gro_receive(head, skb);
}

#define SECONDS_PER_DAY 86400

/* inet_current_timestamp - Return IP network timestamp
 *
 * Return milliseconds since midnight in network byte order.
 */
__be32 inet_current_timestamp(void)
{
        u32 secs;
        u32 msecs;
        struct timespec64 ts;

        ktime_get_real_ts64(&ts);

        /* Get secs since midnight. */
        (void)div_u64_rem(ts.tv_sec, SECONDS_PER_DAY, &secs);
        /* Convert to msecs. */
        msecs = secs * MSEC_PER_SEC;
        /* Convert nsec to msec. */
        msecs += (u32)ts.tv_nsec / NSEC_PER_MSEC;

        /* Convert to network byte order. */
        return htonl(msecs);
}
EXPORT_SYMBOL(inet_current_timestamp);

int inet_recv_error(struct sock *sk, struct msghdr *msg, int len, int *addr_len)
{
        if (sk->sk_family == AF_INET)
                return ip_recv_error(sk, msg, len, addr_len);
#if IS_ENABLED(CONFIG_IPV6)
        if (sk->sk_family == AF_INET6)
                return pingv6_ops.ipv6_recv_error(sk, msg, len, addr_len);
#endif
        return -EINVAL;
}

int inet_gro_complete(struct sk_buff *skb, int nhoff)
{
        __be16 newlen = htons(skb->len - nhoff);
        struct iphdr *iph = (struct iphdr *)(skb->data + nhoff);
        const struct net_offload *ops;
        int proto = iph->protocol;
        int err = -ENOSYS;

        if (skb->encapsulation) {
                skb_set_inner_protocol(skb, cpu_to_be16(ETH_P_IP));
                skb_set_inner_network_header(skb, nhoff);
        }

        csum_replace2(&iph->check, iph->tot_len, newlen);
        iph->tot_len = newlen;

        rcu_read_lock();
        ops = rcu_dereference(inet_offloads[proto]);
        if (WARN_ON(!ops || !ops->callbacks.gro_complete))
                goto out_unlock;

        /* Only need to add sizeof(*iph) to get to the next hdr below
         * because any hdr with option will have been flushed in
         * inet_gro_receive().
         */
        err = INDIRECT_CALL_2(ops->callbacks.gro_complete,
                              tcp4_gro_complete, udp4_gro_complete,
                              skb, nhoff + sizeof(*iph));

out_unlock:
        rcu_read_unlock();

        return err;
}

static int ipip_gro_complete(struct sk_buff *skb, int nhoff)
{
        skb->encapsulation = 1;
        skb_shinfo(skb)->gso_type |= SKB_GSO_IPXIP4;
        return inet_gro_complete(skb, nhoff);
}

int inet_ctl_sock_create(struct sock **sk, unsigned short family,
                         unsigned short type, unsigned char protocol,
                         struct net *net)
{
        struct socket *sock;
        int rc = sock_create_kern(net, family, type, protocol, &sock);

        if (rc == 0) {
                *sk = sock->sk;
                (*sk)->sk_allocation = GFP_ATOMIC;
                /*
                 * Unhash it so that IP input processing does not even see it,
                 * we do not wish this socket to see incoming packets.
                 */
                (*sk)->sk_prot->unhash(*sk);
        }
        return rc;
}
EXPORT_SYMBOL_GPL(inet_ctl_sock_create);

u64 snmp_get_cpu_field(void __percpu *mib, int cpu, int offt)
{
        return  *(((unsigned long *)per_cpu_ptr(mib, cpu)) + offt);
}
EXPORT_SYMBOL_GPL(snmp_get_cpu_field);

unsigned long snmp_fold_field(void __percpu *mib, int offt)
{
        unsigned long res = 0;
        int i;

        for_each_possible_cpu(i)
                res += snmp_get_cpu_field(mib, i, offt);
        return res;
}
EXPORT_SYMBOL_GPL(snmp_fold_field);

#if BITS_PER_LONG==32

u64 snmp_get_cpu_field64(void __percpu *mib, int cpu, int offt,
                         size_t syncp_offset)
{
        void *bhptr;
        struct u64_stats_sync *syncp;
        u64 v;
        unsigned int start;

        bhptr = per_cpu_ptr(mib, cpu);
        syncp = (struct u64_stats_sync *)(bhptr + syncp_offset);
        do {
                start = u64_stats_fetch_begin_irq(syncp);
                v = *(((u64 *)bhptr) + offt);
        } while (u64_stats_fetch_retry_irq(syncp, start));

        return v;
}
EXPORT_SYMBOL_GPL(snmp_get_cpu_field64);

u64 snmp_fold_field64(void __percpu *mib, int offt, size_t syncp_offset)
{
        u64 res = 0;
        int cpu;

        for_each_possible_cpu(cpu) {
                res += snmp_get_cpu_field64(mib, cpu, offt, syncp_offset);
        }
        return res;
}
EXPORT_SYMBOL_GPL(snmp_fold_field64);
#endif

#ifdef CONFIG_IP_MULTICAST
static const struct net_protocol igmp_protocol = {
        .handler =      igmp_rcv,
        .netns_ok =     1,
};
#endif

/* thinking of making this const? Don't.
 * early_demux can change based on sysctl.
 */
static struct net_protocol tcp_protocol = {
        .early_demux    =       tcp_v4_early_demux,
        .early_demux_handler =  tcp_v4_early_demux,
        .handler        =       tcp_v4_rcv,
        .err_handler    =       tcp_v4_err,
        .no_policy      =       1,
        .netns_ok       =       1,
        .icmp_strict_tag_validation = 1,
};

/* thinking of making this const? Don't.
 * early_demux can change based on sysctl.
 */
static struct net_protocol udp_protocol = {
        .early_demux =  udp_v4_early_demux,
        .early_demux_handler =  udp_v4_early_demux,
        .handler =      udp_rcv,
        .err_handler =  udp_err,
        .no_policy =    1,
        .netns_ok =     1,
};

static const struct net_protocol icmp_protocol = {
        .handler =      icmp_rcv,
        .err_handler =  icmp_err,
        .no_policy =    1,
        .netns_ok =     1,
};

static __net_init int ipv4_mib_init_net(struct net *net)
{
        int i;

        net->mib.tcp_statistics = alloc_percpu(struct tcp_mib);
        if (!net->mib.tcp_statistics)
                goto err_tcp_mib;
        net->mib.ip_statistics = alloc_percpu(struct ipstats_mib);
        if (!net->mib.ip_statistics)
                goto err_ip_mib;

        for_each_possible_cpu(i) {
                struct ipstats_mib *af_inet_stats;
                af_inet_stats = per_cpu_ptr(net->mib.ip_statistics, i);
                u64_stats_init(&af_inet_stats->syncp);
        }

        net->mib.net_statistics = alloc_percpu(struct linux_mib);
        if (!net->mib.net_statistics)
                goto err_net_mib;
        net->mib.udp_statistics = alloc_percpu(struct udp_mib);
        if (!net->mib.udp_statistics)
                goto err_udp_mib;
        net->mib.udplite_statistics = alloc_percpu(struct udp_mib);
        if (!net->mib.udplite_statistics)
                goto err_udplite_mib;
        net->mib.icmp_statistics = alloc_percpu(struct icmp_mib);
        if (!net->mib.icmp_statistics)
                goto err_icmp_mib;
        net->mib.icmpmsg_statistics = kzalloc(sizeof(struct icmpmsg_mib),
                                              GFP_KERNEL);
        if (!net->mib.icmpmsg_statistics)
                goto err_icmpmsg_mib;

        tcp_mib_init(net);
        return 0;

err_icmpmsg_mib:
        free_percpu(net->mib.icmp_statistics);
err_icmp_mib:
        free_percpu(net->mib.udplite_statistics);
err_udplite_mib:
        free_percpu(net->mib.udp_statistics);
err_udp_mib:
        free_percpu(net->mib.net_statistics);
err_net_mib:
        free_percpu(net->mib.ip_statistics);
err_ip_mib:
        free_percpu(net->mib.tcp_statistics);
err_tcp_mib:
        return -ENOMEM;
}

static __net_exit void ipv4_mib_exit_net(struct net *net)
{
        kfree(net->mib.icmpmsg_statistics);
        free_percpu(net->mib.icmp_statistics);
        free_percpu(net->mib.udplite_statistics);
        free_percpu(net->mib.udp_statistics);
        free_percpu(net->mib.net_statistics);
        free_percpu(net->mib.ip_statistics);
        free_percpu(net->mib.tcp_statistics);
#ifdef CONFIG_MPTCP
        /* allocated on demand, see mptcp_init_sock() */
        free_percpu(net->mib.mptcp_statistics);
#endif
}

static __net_initdata struct pernet_operations ipv4_mib_ops = {
        .init = ipv4_mib_init_net,
        .exit = ipv4_mib_exit_net,
};

static int __init init_ipv4_mibs(void)
{
        return register_pernet_subsys(&ipv4_mib_ops);
}

static __net_init int inet_init_net(struct net *net)
{
        /*
         * Set defaults for local port range
         */
        seqlock_init(&net->ipv4.ip_local_ports.lock);
        net->ipv4.ip_local_ports.range[0] =  32768;
        net->ipv4.ip_local_ports.range[1] =  60999;

        seqlock_init(&net->ipv4.ping_group_range.lock);
        /*
         * Sane defaults - nobody may create ping sockets.
         * Boot scripts should set this to distro-specific group.
         */
        net->ipv4.ping_group_range.range[0] = make_kgid(&init_user_ns, 1);
        net->ipv4.ping_group_range.range[1] = make_kgid(&init_user_ns, 0);

        /* Default values for sysctl-controlled parameters.
         * We set them here, in case sysctl is not compiled.
         */
        net->ipv4.sysctl_ip_default_ttl = IPDEFTTL;
        net->ipv4.sysctl_ip_fwd_update_priority = 1;
        net->ipv4.sysctl_ip_dynaddr = 0;
        net->ipv4.sysctl_ip_early_demux = 1;
        net->ipv4.sysctl_udp_early_demux = 1;
        net->ipv4.sysctl_tcp_early_demux = 1;
        net->ipv4.sysctl_nexthop_compat_mode = 1;
#ifdef CONFIG_SYSCTL
        net->ipv4.sysctl_ip_prot_sock = PROT_SOCK;
#endif

        /* Some igmp sysctl, whose values are always used */
        net->ipv4.sysctl_igmp_max_memberships = 20;
        net->ipv4.sysctl_igmp_max_msf = 10;
        /* IGMP reports for link-local multicast groups are enabled by default */
        net->ipv4.sysctl_igmp_llm_reports = 1;
        net->ipv4.sysctl_igmp_qrv = 2;

        net->ipv4.sysctl_fib_notify_on_flag_change = 0;

        return 0;
}

static __net_initdata struct pernet_operations af_inet_ops = {
        .init = inet_init_net,
};

static int __init init_inet_pernet_ops(void)
{
        return register_pernet_subsys(&af_inet_ops);
}

static int ipv4_proc_init(void);

/*
 *      IP protocol layer initialiser
 */

static struct packet_offload ip_packet_offload __read_mostly = {
        .type = cpu_to_be16(ETH_P_IP),
        .callbacks = {
                .gso_segment = inet_gso_segment,
                .gro_receive = inet_gro_receive,
                .gro_complete = inet_gro_complete,
        },
};

static const struct net_offload ipip_offload = {
        .callbacks = {
                .gso_segment    = ipip_gso_segment,
                .gro_receive    = ipip_gro_receive,
                .gro_complete   = ipip_gro_complete,
        },
};

static int __init ipip_offload_init(void)
{
        return inet_add_offload(&ipip_offload, IPPROTO_IPIP);
}

static int __init ipv4_offload_init(void)
{
        /*
         * Add offloads
         */
        if (udpv4_offload_init() < 0)
                pr_crit("%s: Cannot add UDP protocol offload\n", __func__);
        if (tcpv4_offload_init() < 0)
                pr_crit("%s: Cannot add TCP protocol offload\n", __func__);
        if (ipip_offload_init() < 0)
                pr_crit("%s: Cannot add IPIP protocol offload\n", __func__);

        dev_add_offload(&ip_packet_offload);
        return 0;
}

fs_initcall(ipv4_offload_init);

static struct packet_type ip_packet_type __read_mostly = {
        .type = cpu_to_be16(ETH_P_IP),
        .func = ip_rcv,
        .list_func = ip_list_rcv,
};

static int __init inet_init(void)
{
        struct inet_protosw *q;
        struct list_head *r;
        int rc;

        sock_skb_cb_check_size(sizeof(struct inet_skb_parm));

        rc = proto_register(&tcp_prot, 1);
        if (rc)
                goto out;

        rc = proto_register(&udp_prot, 1);
        if (rc)
                goto out_unregister_tcp_proto;

        rc = proto_register(&raw_prot, 1);
        if (rc)
                goto out_unregister_udp_proto;

        rc = proto_register(&ping_prot, 1);
        if (rc)
                goto out_unregister_raw_proto;

        /*
         *      Tell SOCKET that we are alive...
         */

        (void)sock_register(&inet_family_ops);

#ifdef CONFIG_SYSCTL
        ip_static_sysctl_init();
#endif

        /*
         *      Add all the base protocols.
         */

        if (inet_add_protocol(&icmp_protocol, IPPROTO_ICMP) < 0)
                pr_crit("%s: Cannot add ICMP protocol\n", __func__);
        if (inet_add_protocol(&udp_protocol, IPPROTO_UDP) < 0)
                pr_crit("%s: Cannot add UDP protocol\n", __func__);
        if (inet_add_protocol(&tcp_protocol, IPPROTO_TCP) < 0)
                pr_crit("%s: Cannot add TCP protocol\n", __func__);
#ifdef CONFIG_IP_MULTICAST
        if (inet_add_protocol(&igmp_protocol, IPPROTO_IGMP) < 0)
                pr_crit("%s: Cannot add IGMP protocol\n", __func__);
#endif

        /* Register the socket-side information for inet_create. */
        for (r = &inetsw[0]; r < &inetsw[SOCK_MAX]; ++r)
                INIT_LIST_HEAD(r);

        for (q = inetsw_array; q < &inetsw_array[INETSW_ARRAY_LEN]; ++q)
                inet_register_protosw(q);

        /*
         *      Set the ARP module up
         */

        arp_init();

        /*
         *      Set the IP module up
         */

        ip_init();

        /* Setup TCP slab cache for open requests. */
        tcp_init();

        /* Setup UDP memory threshold */
        udp_init();

        /* Add UDP-Lite (RFC 3828) */
        udplite4_register();

        raw_init();

        ping_init();

        /*
         *      Set the ICMP layer up
         */

        if (icmp_init() < 0)
                panic("Failed to create the ICMP control socket.\n");

        /*
         *      Initialise the multicast router
         */
#if defined(CONFIG_IP_MROUTE)
        if (ip_mr_init())
                pr_crit("%s: Cannot init ipv4 mroute\n", __func__);
#endif

        if (init_inet_pernet_ops())
                pr_crit("%s: Cannot init ipv4 inet pernet ops\n", __func__);
        /*
         *      Initialise per-cpu ipv4 mibs
         */

        if (init_ipv4_mibs())
                pr_crit("%s: Cannot init ipv4 mibs\n", __func__);

        ipv4_proc_init();

        ipfrag_init();

        dev_add_pack(&ip_packet_type);

        ip_tunnel_core_init();

        rc = 0;
out:
        return rc;
out_unregister_raw_proto:
        proto_unregister(&raw_prot);
out_unregister_udp_proto:
        proto_unregister(&udp_prot);
out_unregister_tcp_proto:
        proto_unregister(&tcp_prot);
        goto out;
}

fs_initcall(inet_init);

/* ------------------------------------------------------------------------ */

#ifdef CONFIG_PROC_FS
static int __init ipv4_proc_init(void)
{
        int rc = 0;

        if (raw_proc_init())
                goto out_raw;
        if (tcp4_proc_init())
                goto out_tcp;
        if (udp4_proc_init())
                goto out_udp;
        if (ping_proc_init())
                goto out_ping;
        if (ip_misc_proc_init())
                goto out_misc;
out:
        return rc;
out_misc:
        ping_proc_exit();
out_ping:
        udp4_proc_exit();
out_udp:
        tcp4_proc_exit();
out_tcp:
        raw_proc_exit();
out_raw:
        rc = -ENOMEM;
        goto out;
}

#else /* CONFIG_PROC_FS */
static int __init ipv4_proc_init(void)
{
        return 0;
}
#endif /* CONFIG_PROC_FS */