// SPDX-License-Identifier: GPL-2.0
/* Copyright (c) 2020 Facebook */
#include "bpf_iter.h"
#include "bpf_tracing_net.h"
#include <bpf/bpf_helpers.h>
#include <bpf/bpf_endian.h>

char _license[] SEC("license") = "GPL";

static int hlist_unhashed_lockless(const struct hlist_node *h)
{
        return !(h->pprev);
}

static int timer_pending(const struct timer_list * timer)
{
        return !hlist_unhashed_lockless(&timer->entry);
}

extern unsigned CONFIG_HZ __kconfig;

#define USER_HZ         100
#define NSEC_PER_SEC    1000000000ULL
static clock_t jiffies_to_clock_t(unsigned long x)
{
        /* The implementation here tailored to a particular
         * setting of USER_HZ.
         */
        u64 tick_nsec = (NSEC_PER_SEC + CONFIG_HZ/2) / CONFIG_HZ;
        u64 user_hz_nsec = NSEC_PER_SEC / USER_HZ;

        if ((tick_nsec % user_hz_nsec) == 0) {
                if (CONFIG_HZ < USER_HZ)
                        return x * (USER_HZ / CONFIG_HZ);
                else
                        return x / (CONFIG_HZ / USER_HZ);
        }
        return x * tick_nsec/user_hz_nsec;
}

static clock_t jiffies_delta_to_clock_t(long delta)
{
        if (delta <= 0)
                return 0;

        return jiffies_to_clock_t(delta);
}

static long sock_i_ino(const struct sock *sk)
{
        const struct socket *sk_socket = sk->sk_socket;
        const struct inode *inode;
        unsigned long ino;

        if (!sk_socket)
                return 0;

        inode = &container_of(sk_socket, struct socket_alloc, socket)->vfs_inode;
        bpf_probe_read_kernel(&ino, sizeof(ino), &inode->i_ino);
        return ino;
}

static bool
inet_csk_in_pingpong_mode(const struct inet_connection_sock *icsk)
{
        return icsk->icsk_ack.pingpong >= TCP_PINGPONG_THRESH;
}

static bool tcp_in_initial_slowstart(const struct tcp_sock *tcp)
{
        return tcp->snd_ssthresh >= TCP_INFINITE_SSTHRESH;
}

static int dump_tcp_sock(struct seq_file *seq, struct tcp_sock *tp,
                         uid_t uid, __u32 seq_num)
{
        const struct inet_connection_sock *icsk;
        const struct fastopen_queue *fastopenq;
        const struct inet_sock *inet;
        unsigned long timer_expires;
        const struct sock *sp;
        __u16 destp, srcp;
        __be32 dest, src;
        int timer_active;
        int rx_queue;
        int state;

        icsk = &tp->inet_conn;
        inet = &icsk->icsk_inet;
        sp = &inet->sk;
        fastopenq = &icsk->icsk_accept_queue.fastopenq;

        dest = inet->inet_daddr;
        src = inet->inet_rcv_saddr;
        destp = bpf_ntohs(inet->inet_dport);
        srcp = bpf_ntohs(inet->inet_sport);

        if (icsk->icsk_pending == ICSK_TIME_RETRANS ||
            icsk->icsk_pending == ICSK_TIME_REO_TIMEOUT ||
            icsk->icsk_pending == ICSK_TIME_LOSS_PROBE) {
                timer_active = 1;
                timer_expires = icsk->icsk_timeout;
        } else if (icsk->icsk_pending == ICSK_TIME_PROBE0) {
                timer_active = 4;
                timer_expires = icsk->icsk_timeout;
        } else if (timer_pending(&sp->sk_timer)) {
                timer_active = 2;
                timer_expires = sp->sk_timer.expires;
        } else {
                timer_active = 0;
                timer_expires = bpf_jiffies64();
        }

        state = sp->sk_state;
        if (state == TCP_LISTEN) {
                rx_queue = sp->sk_ack_backlog;
        } else {
                rx_queue = tp->rcv_nxt - tp->copied_seq;
                if (rx_queue < 0)
                        rx_queue = 0;
        }

        BPF_SEQ_PRINTF(seq, "%4d: %08X:%04X %08X:%04X ",
                       seq_num, src, srcp, dest, destp);
        BPF_SEQ_PRINTF(seq, "%02X %08X:%08X %02X:%08lX %08X %5u %8d %lu %d ",
                       state,
                       tp->write_seq - tp->snd_una, rx_queue,
                       timer_active,
                       jiffies_delta_to_clock_t(timer_expires - bpf_jiffies64()),
                       icsk->icsk_retransmits, uid,
                       icsk->icsk_probes_out,
                       sock_i_ino(sp),
                       sp->sk_refcnt.refs.counter);
        BPF_SEQ_PRINTF(seq, "%pK %lu %lu %u %u %d\n",
                       tp,
                       jiffies_to_clock_t(icsk->icsk_rto),
                       jiffies_to_clock_t(icsk->icsk_ack.ato),
                       (icsk->icsk_ack.quick << 1) | inet_csk_in_pingpong_mode(icsk),
                       tp->snd_cwnd,
                       state == TCP_LISTEN ? fastopenq->max_qlen
                                : (tcp_in_initial_slowstart(tp) ? -1 : tp->snd_ssthresh)
                      );

        return 0;
}

static int dump_tw_sock(struct seq_file *seq, struct tcp_timewait_sock *ttw,
                        uid_t uid, __u32 seq_num)
{
        struct inet_timewait_sock *tw = &ttw->tw_sk;
        __u16 destp, srcp;
        __be32 dest, src;
        long delta;

        delta = tw->tw_timer.expires - bpf_jiffies64();
        dest = tw->tw_daddr;
        src  = tw->tw_rcv_saddr;
        destp = bpf_ntohs(tw->tw_dport);
        srcp  = bpf_ntohs(tw->tw_sport);

        BPF_SEQ_PRINTF(seq, "%4d: %08X:%04X %08X:%04X ",
                       seq_num, src, srcp, dest, destp);

        BPF_SEQ_PRINTF(seq, "%02X %08X:%08X %02X:%08lX %08X %5d %8d %d %d %pK\n",
                       tw->tw_substate, 0, 0,
                       3, jiffies_delta_to_clock_t(delta), 0, 0, 0, 0,
                       tw->tw_refcnt.refs.counter, tw);

        return 0;
}

static int dump_req_sock(struct seq_file *seq, struct tcp_request_sock *treq,
                         uid_t uid, __u32 seq_num)
{
        struct inet_request_sock *irsk = &treq->req;
        struct request_sock *req = &irsk->req;
        long ttd;

        ttd = req->rsk_timer.expires - bpf_jiffies64();

        if (ttd < 0)
                ttd = 0;

        BPF_SEQ_PRINTF(seq, "%4d: %08X:%04X %08X:%04X ",
                       seq_num, irsk->ir_loc_addr,
                       irsk->ir_num, irsk->ir_rmt_addr,
                       bpf_ntohs(irsk->ir_rmt_port));
        BPF_SEQ_PRINTF(seq, "%02X %08X:%08X %02X:%08lX %08X %5d %8d %d %d %pK\n",
                       TCP_SYN_RECV, 0, 0, 1, jiffies_to_clock_t(ttd),
                       req->num_timeout, uid, 0, 0, 0, req);

        return 0;
}

SEC("iter/tcp")
int dump_tcp4(struct bpf_iter__tcp *ctx)
{
        struct sock_common *sk_common = ctx->sk_common;
        struct seq_file *seq = ctx->meta->seq;
        struct tcp_timewait_sock *tw;
        struct tcp_request_sock *req;
        struct tcp_sock *tp;
        uid_t uid = ctx->uid;
        __u32 seq_num;

        if (sk_common == (void *)0)
                return 0;

        seq_num = ctx->meta->seq_num;
        if (seq_num == 0)
                BPF_SEQ_PRINTF(seq, "  sl  "
                                    "local_address "
                                    "rem_address   "
                                    "st tx_queue rx_queue tr tm->when retrnsmt"
                                    "   uid  timeout inode\n");

        if (sk_common->skc_family != AF_INET)
                return 0;

        tp = bpf_skc_to_tcp_sock(sk_common);
        if (tp)
                return dump_tcp_sock(seq, tp, uid, seq_num);

        tw = bpf_skc_to_tcp_timewait_sock(sk_common);
        if (tw)
                return dump_tw_sock(seq, tw, uid, seq_num);

        req = bpf_skc_to_tcp_request_sock(sk_common);
        if (req)
                return dump_req_sock(seq, req, uid, seq_num);

        return 0;
}