// SPDX-License-Identifier: GPL-2.0-or-later
/* incoming call handling
 *
 * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells (dhowells@redhat.com)
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/module.h>
#include <linux/net.h>
#include <linux/skbuff.h>
#include <linux/errqueue.h>
#include <linux/udp.h>
#include <linux/in.h>
#include <linux/in6.h>
#include <linux/icmp.h>
#include <linux/gfp.h>
#include <linux/circ_buf.h>
#include <net/sock.h>
#include <net/af_rxrpc.h>
#include <net/ip.h>
#include "ar-internal.h"

static void rxrpc_dummy_notify(struct sock *sk, struct rxrpc_call *call,
                               unsigned long user_call_ID)
{
}

/*
 * Preallocate a single service call, connection and peer and, if possible,
 * give them a user ID and attach the user's side of the ID to them.
 */
static int rxrpc_service_prealloc_one(struct rxrpc_sock *rx,
                                      struct rxrpc_backlog *b,
                                      rxrpc_notify_rx_t notify_rx,
                                      rxrpc_user_attach_call_t user_attach_call,
                                      unsigned long user_call_ID, gfp_t gfp,
                                      unsigned int debug_id)
{
        const void *here = __builtin_return_address(0);
        struct rxrpc_call *call, *xcall;
        struct rxrpc_net *rxnet = rxrpc_net(sock_net(&rx->sk));
        struct rb_node *parent, **pp;
        int max, tmp;
        unsigned int size = RXRPC_BACKLOG_MAX;
        unsigned int head, tail, call_head, call_tail;

        max = rx->sk.sk_max_ack_backlog;
        tmp = rx->sk.sk_ack_backlog;
        if (tmp >= max) {
                _leave(" = -ENOBUFS [full %u]", max);
                return -ENOBUFS;
        }
        max -= tmp;

        /* We don't need more conns and peers than we have calls, but on the
         * other hand, we shouldn't ever use more peers than conns or conns
         * than calls.
         */
        call_head = b->call_backlog_head;
        call_tail = READ_ONCE(b->call_backlog_tail);
        tmp = CIRC_CNT(call_head, call_tail, size);
        if (tmp >= max) {
                _leave(" = -ENOBUFS [enough %u]", tmp);
                return -ENOBUFS;
        }
        max = tmp + 1;

        head = b->peer_backlog_head;
        tail = READ_ONCE(b->peer_backlog_tail);
        if (CIRC_CNT(head, tail, size) < max) {
                struct rxrpc_peer *peer = rxrpc_alloc_peer(rx->local, gfp);
                if (!peer)
                        return -ENOMEM;
                b->peer_backlog[head] = peer;
                smp_store_release(&b->peer_backlog_head,
                                  (head + 1) & (size - 1));
        }

        head = b->conn_backlog_head;
        tail = READ_ONCE(b->conn_backlog_tail);
        if (CIRC_CNT(head, tail, size) < max) {
                struct rxrpc_connection *conn;

                conn = rxrpc_prealloc_service_connection(rxnet, gfp);
                if (!conn)
                        return -ENOMEM;
                b->conn_backlog[head] = conn;
                smp_store_release(&b->conn_backlog_head,
                                  (head + 1) & (size - 1));

                trace_rxrpc_conn(conn->debug_id, rxrpc_conn_new_service,
                                 atomic_read(&conn->usage), here);
        }

        /* Now it gets complicated, because calls get registered with the
         * socket here, with a user ID preassigned by the user.
         */
        call = rxrpc_alloc_call(rx, gfp, debug_id);
        if (!call)
                return -ENOMEM;
        call->flags |= (1 << RXRPC_CALL_IS_SERVICE);
        call->state = RXRPC_CALL_SERVER_PREALLOC;

        trace_rxrpc_call(call->debug_id, rxrpc_call_new_service,
                         atomic_read(&call->usage),
                         here, (const void *)user_call_ID);

        write_lock(&rx->call_lock);

        /* Check the user ID isn't already in use */
        pp = &rx->calls.rb_node;
        parent = NULL;
        while (*pp) {
                parent = *pp;
                xcall = rb_entry(parent, struct rxrpc_call, sock_node);
                if (user_call_ID < xcall->user_call_ID)
                        pp = &(*pp)->rb_left;
                else if (user_call_ID > xcall->user_call_ID)
                        pp = &(*pp)->rb_right;
                else
                        goto id_in_use;
        }

        call->user_call_ID = user_call_ID;
        call->notify_rx = notify_rx;
        if (user_attach_call) {
                rxrpc_get_call(call, rxrpc_call_got_kernel);
                user_attach_call(call, user_call_ID);
        }

        rxrpc_get_call(call, rxrpc_call_got_userid);
        rb_link_node(&call->sock_node, parent, pp);
        rb_insert_color(&call->sock_node, &rx->calls);
        set_bit(RXRPC_CALL_HAS_USERID, &call->flags);

        list_add(&call->sock_link, &rx->sock_calls);

        write_unlock(&rx->call_lock);

        rxnet = call->rxnet;
        write_lock(&rxnet->call_lock);
        list_add_tail(&call->link, &rxnet->calls);
        write_unlock(&rxnet->call_lock);

        b->call_backlog[call_head] = call;
        smp_store_release(&b->call_backlog_head, (call_head + 1) & (size - 1));
        _leave(" = 0 [%d -> %lx]", call->debug_id, user_call_ID);
        return 0;

id_in_use:
        write_unlock(&rx->call_lock);
        rxrpc_cleanup_call(call);
        _leave(" = -EBADSLT");
        return -EBADSLT;
}

/*
 * Allocate the preallocation buffers for incoming service calls.  These must
 * be charged manually.
 */
int rxrpc_service_prealloc(struct rxrpc_sock *rx, gfp_t gfp)
{
        struct rxrpc_backlog *b = rx->backlog;

        if (!b) {
                b = kzalloc(sizeof(struct rxrpc_backlog), gfp);
                if (!b)
                        return -ENOMEM;
                rx->backlog = b;
        }

        return 0;
}

/*
 * Discard the preallocation on a service.
 */
void rxrpc_discard_prealloc(struct rxrpc_sock *rx)
{
        struct rxrpc_backlog *b = rx->backlog;
        struct rxrpc_net *rxnet = rxrpc_net(sock_net(&rx->sk));
        unsigned int size = RXRPC_BACKLOG_MAX, head, tail;

        if (!b)
                return;
        rx->backlog = NULL;

        /* Make sure that there aren't any incoming calls in progress before we
         * clear the preallocation buffers.
         */
        spin_lock_bh(&rx->incoming_lock);
        spin_unlock_bh(&rx->incoming_lock);

        head = b->peer_backlog_head;
        tail = b->peer_backlog_tail;
        while (CIRC_CNT(head, tail, size) > 0) {
                struct rxrpc_peer *peer = b->peer_backlog[tail];
                rxrpc_put_local(peer->local);
                kfree(peer);
                tail = (tail + 1) & (size - 1);
        }

        head = b->conn_backlog_head;
        tail = b->conn_backlog_tail;
        while (CIRC_CNT(head, tail, size) > 0) {
                struct rxrpc_connection *conn = b->conn_backlog[tail];
                write_lock(&rxnet->conn_lock);
                list_del(&conn->link);
                list_del(&conn->proc_link);
                write_unlock(&rxnet->conn_lock);
                kfree(conn);
                if (atomic_dec_and_test(&rxnet->nr_conns))
                        wake_up_var(&rxnet->nr_conns);
                tail = (tail + 1) & (size - 1);
        }

        head = b->call_backlog_head;
        tail = b->call_backlog_tail;
        while (CIRC_CNT(head, tail, size) > 0) {
                struct rxrpc_call *call = b->call_backlog[tail];
                rcu_assign_pointer(call->socket, rx);
                if (rx->discard_new_call) {
                        _debug("discard %lx", call->user_call_ID);
                        rx->discard_new_call(call, call->user_call_ID);
                        if (call->notify_rx)
                                call->notify_rx = rxrpc_dummy_notify;
                        rxrpc_put_call(call, rxrpc_call_put_kernel);
                }
                rxrpc_call_completed(call);
                rxrpc_release_call(rx, call);
                rxrpc_put_call(call, rxrpc_call_put);
                tail = (tail + 1) & (size - 1);
        }

        kfree(b);
}

/*
 * Ping the other end to fill our RTT cache and to retrieve the rwind
 * and MTU parameters.
 */
static void rxrpc_send_ping(struct rxrpc_call *call, struct sk_buff *skb)
{
        struct rxrpc_skb_priv *sp = rxrpc_skb(skb);
        ktime_t now = skb->tstamp;

        if (call->peer->rtt_count < 3 ||
            ktime_before(ktime_add_ms(call->peer->rtt_last_req, 1000), now))
                rxrpc_propose_ACK(call, RXRPC_ACK_PING, sp->hdr.serial,
                                  true, true,
                                  rxrpc_propose_ack_ping_for_params);
}

/*
 * Allocate a new incoming call from the prealloc pool, along with a connection
 * and a peer as necessary.
 */
static struct rxrpc_call *rxrpc_alloc_incoming_call(struct rxrpc_sock *rx,
                                                    struct rxrpc_local *local,
                                                    struct rxrpc_peer *peer,
                                                    struct rxrpc_connection *conn,
                                                    const struct rxrpc_security *sec,
                                                    struct sk_buff *skb)
{
        struct rxrpc_backlog *b = rx->backlog;
        struct rxrpc_call *call;
        unsigned short call_head, conn_head, peer_head;
        unsigned short call_tail, conn_tail, peer_tail;
        unsigned short call_count, conn_count;

        /* #calls >= #conns >= #peers must hold true. */
        call_head = smp_load_acquire(&b->call_backlog_head);
        call_tail = b->call_backlog_tail;
        call_count = CIRC_CNT(call_head, call_tail, RXRPC_BACKLOG_MAX);
        conn_head = smp_load_acquire(&b->conn_backlog_head);
        conn_tail = b->conn_backlog_tail;
        conn_count = CIRC_CNT(conn_head, conn_tail, RXRPC_BACKLOG_MAX);
        ASSERTCMP(conn_count, >=, call_count);
        peer_head = smp_load_acquire(&b->peer_backlog_head);
        peer_tail = b->peer_backlog_tail;
        ASSERTCMP(CIRC_CNT(peer_head, peer_tail, RXRPC_BACKLOG_MAX), >=,
                  conn_count);

        if (call_count == 0)
                return NULL;

        if (!conn) {
                if (peer && !rxrpc_get_peer_maybe(peer))
                        peer = NULL;
                if (!peer) {
                        peer = b->peer_backlog[peer_tail];
                        if (rxrpc_extract_addr_from_skb(&peer->srx, skb) < 0)
                                return NULL;
                        b->peer_backlog[peer_tail] = NULL;
                        smp_store_release(&b->peer_backlog_tail,
                                          (peer_tail + 1) &
                                          (RXRPC_BACKLOG_MAX - 1));

                        rxrpc_new_incoming_peer(rx, local, peer);
                }

                /* Now allocate and set up the connection */
                conn = b->conn_backlog[conn_tail];
                b->conn_backlog[conn_tail] = NULL;
                smp_store_release(&b->conn_backlog_tail,
                                  (conn_tail + 1) & (RXRPC_BACKLOG_MAX - 1));
                conn->params.local = rxrpc_get_local(local);
                conn->params.peer = peer;
                rxrpc_see_connection(conn);
                rxrpc_new_incoming_connection(rx, conn, sec, skb);
        } else {
                rxrpc_get_connection(conn);
        }

        /* And now we can allocate and set up a new call */
        call = b->call_backlog[call_tail];
        b->call_backlog[call_tail] = NULL;
        smp_store_release(&b->call_backlog_tail,
                          (call_tail + 1) & (RXRPC_BACKLOG_MAX - 1));

        rxrpc_see_call(call);
        call->conn = conn;
        call->security = conn->security;
        call->security_ix = conn->security_ix;
        call->peer = rxrpc_get_peer(conn->params.peer);
        call->cong_cwnd = call->peer->cong_cwnd;
        return call;
}

/*
 * Set up a new incoming call.  Called in BH context with the RCU read lock
 * held.
 *
 * If this is for a kernel service, when we allocate the call, it will have
 * three refs on it: (1) the kernel service, (2) the user_call_ID tree, (3) the
 * retainer ref obtained from the backlog buffer.  Prealloc calls for userspace
 * services only have the ref from the backlog buffer.  We want to pass this
 * ref to non-BH context to dispose of.
 *
 * If we want to report an error, we mark the skb with the packet type and
 * abort code and return NULL.
 *
 * The call is returned with the user access mutex held.
 */
struct rxrpc_call *rxrpc_new_incoming_call(struct rxrpc_local *local,
                                           struct rxrpc_sock *rx,
                                           struct sk_buff *skb)
{
        struct rxrpc_skb_priv *sp = rxrpc_skb(skb);
        const struct rxrpc_security *sec = NULL;
        struct rxrpc_connection *conn;
        struct rxrpc_peer *peer = NULL;
        struct rxrpc_call *call = NULL;

        _enter("");

        spin_lock(&rx->incoming_lock);
        if (rx->sk.sk_state == RXRPC_SERVER_LISTEN_DISABLED ||
            rx->sk.sk_state == RXRPC_CLOSE) {
                trace_rxrpc_abort(0, "CLS", sp->hdr.cid, sp->hdr.callNumber,
                                  sp->hdr.seq, RX_INVALID_OPERATION, ESHUTDOWN);
                skb->mark = RXRPC_SKB_MARK_REJECT_ABORT;
                skb->priority = RX_INVALID_OPERATION;
                goto no_call;
        }

        /* The peer, connection and call may all have sprung into existence due
         * to a duplicate packet being handled on another CPU in parallel, so
         * we have to recheck the routing.  However, we're now holding
         * rx->incoming_lock, so the values should remain stable.
         */
        conn = rxrpc_find_connection_rcu(local, skb, &peer);

        if (!conn) {
                sec = rxrpc_get_incoming_security(rx, skb);
                if (!sec)
                        goto no_call;
        }

        call = rxrpc_alloc_incoming_call(rx, local, peer, conn, sec, skb);
        if (!call) {
                skb->mark = RXRPC_SKB_MARK_REJECT_BUSY;
                goto no_call;
        }

        trace_rxrpc_receive(call, rxrpc_receive_incoming,
                            sp->hdr.serial, sp->hdr.seq);

        /* Make the call live. */
        rxrpc_incoming_call(rx, call, skb);
        conn = call->conn;

        if (rx->notify_new_call)
                rx->notify_new_call(&rx->sk, call, call->user_call_ID);

        spin_lock(&conn->state_lock);
        switch (conn->state) {
        case RXRPC_CONN_SERVICE_UNSECURED:
                conn->state = RXRPC_CONN_SERVICE_CHALLENGING;
                set_bit(RXRPC_CONN_EV_CHALLENGE, &call->conn->events);
                rxrpc_queue_conn(call->conn);
                break;

        case RXRPC_CONN_SERVICE:
                write_lock(&call->state_lock);
                if (call->state < RXRPC_CALL_COMPLETE)
                        call->state = RXRPC_CALL_SERVER_RECV_REQUEST;
                write_unlock(&call->state_lock);
                break;

        case RXRPC_CONN_REMOTELY_ABORTED:
                rxrpc_set_call_completion(call, RXRPC_CALL_REMOTELY_ABORTED,
                                          conn->abort_code, conn->error);
                break;
        case RXRPC_CONN_LOCALLY_ABORTED:
                rxrpc_abort_call("CON", call, sp->hdr.seq,
                                 conn->abort_code, conn->error);
                break;
        default:
                BUG();
        }
        spin_unlock(&conn->state_lock);
        spin_unlock(&rx->incoming_lock);

        rxrpc_send_ping(call, skb);

        /* We have to discard the prealloc queue's ref here and rely on a
         * combination of the RCU read lock and refs held either by the socket
         * (recvmsg queue, to-be-accepted queue or user ID tree) or the kernel
         * service to prevent the call from being deallocated too early.
         */
        rxrpc_put_call(call, rxrpc_call_put);

        _leave(" = %p{%d}", call, call->debug_id);
        return call;

no_call:
        spin_unlock(&rx->incoming_lock);
        _leave(" = NULL [%u]", skb->mark);
        return NULL;
}

/*
 * Charge up socket with preallocated calls, attaching user call IDs.
 */
int rxrpc_user_charge_accept(struct rxrpc_sock *rx, unsigned long user_call_ID)
{
        struct rxrpc_backlog *b = rx->backlog;

        if (rx->sk.sk_state == RXRPC_CLOSE)
                return -ESHUTDOWN;

        return rxrpc_service_prealloc_one(rx, b, NULL, NULL, user_call_ID,
                                          GFP_KERNEL,
                                          atomic_inc_return(&rxrpc_debug_id));
}

/*
 * rxrpc_kernel_charge_accept - Charge up socket with preallocated calls
 * @sock: The socket on which to preallocate
 * @notify_rx: Event notification function for the call
 * @user_attach_call: Func to attach call to user_call_ID
 * @user_call_ID: The tag to attach to the preallocated call
 * @gfp: The allocation conditions.
 * @debug_id: The tracing debug ID.
 *
 * Charge up the socket with preallocated calls, each with a user ID.  A
 * function should be provided to effect the attachment from the user's side.
 * The user is given a ref to hold on the call.
 *
 * Note that the call may be come connected before this function returns.
 */
int rxrpc_kernel_charge_accept(struct socket *sock,
                               rxrpc_notify_rx_t notify_rx,
                               rxrpc_user_attach_call_t user_attach_call,
                               unsigned long user_call_ID, gfp_t gfp,
                               unsigned int debug_id)
{
        struct rxrpc_sock *rx = rxrpc_sk(sock->sk);
        struct rxrpc_backlog *b = rx->backlog;

        if (sock->sk->sk_state == RXRPC_CLOSE)
                return -ESHUTDOWN;

        return rxrpc_service_prealloc_one(rx, b, notify_rx,
                                          user_attach_call, user_call_ID,
                                          gfp, debug_id);
}
EXPORT_SYMBOL(rxrpc_kernel_charge_accept);