// SPDX-License-Identifier: GPL-2.0-or-later
/*
 *      common UDP/RAW code
 *      Linux INET implementation
 *
 * Authors:
 *      Hideaki YOSHIFUJI <yoshfuji@linux-ipv6.org>
 */

#include <linux/types.h>
#include <linux/module.h>
#include <linux/in.h>
#include <net/ip.h>
#include <net/sock.h>
#include <net/route.h>
#include <net/tcp_states.h>
#include <net/sock_reuseport.h>

int __ip4_datagram_connect(struct sock *sk, struct sockaddr_unsized *uaddr, int addr_len)
{
        struct inet_sock *inet = inet_sk(sk);
        struct sockaddr_in *usin = (struct sockaddr_in *) uaddr;
        struct flowi4 *fl4;
        struct rtable *rt;
        __be32 saddr;
        int oif;
        int err;


        if (addr_len < sizeof(*usin))
                return -EINVAL;

        if (usin->sin_family != AF_INET)
                return -EAFNOSUPPORT;

        sk_dst_reset(sk);

        oif = sk->sk_bound_dev_if;
        saddr = inet->inet_saddr;
        if (ipv4_is_multicast(usin->sin_addr.s_addr)) {
                if (!oif || netif_index_is_l3_master(sock_net(sk), oif))
                        oif = READ_ONCE(inet->mc_index);
                if (!saddr)
                        saddr = READ_ONCE(inet->mc_addr);
        } else if (!oif) {
                oif = READ_ONCE(inet->uc_index);
        }
        fl4 = &inet->cork.fl.u.ip4;
        rt = ip_route_connect(fl4, usin->sin_addr.s_addr, saddr, oif,
                              sk->sk_protocol, inet->inet_sport,
                              usin->sin_port, sk);
        if (IS_ERR(rt)) {
                err = PTR_ERR(rt);
                if (err == -ENETUNREACH)
                        IP_INC_STATS(sock_net(sk), IPSTATS_MIB_OUTNOROUTES);
                goto out;
        }

        if ((rt->rt_flags & RTCF_BROADCAST) && !sock_flag(sk, SOCK_BROADCAST)) {
                ip_rt_put(rt);
                err = -EACCES;
                goto out;
        }

        /* Update addresses before rehashing */
        inet->inet_daddr = fl4->daddr;
        inet->inet_dport = usin->sin_port;
        if (!inet->inet_saddr)
                inet->inet_saddr = fl4->saddr;
        if (!inet->inet_rcv_saddr) {
                inet->inet_rcv_saddr = fl4->saddr;
                if (sk->sk_prot->rehash)
                        sk->sk_prot->rehash(sk);
        }
        reuseport_has_conns_set(sk);
        sk->sk_state = TCP_ESTABLISHED;
        sk_set_txhash(sk);
        atomic_set(&inet->inet_id, get_random_u16());

        sk_dst_set(sk, &rt->dst);
        err = 0;
out:
        return err;
}
EXPORT_SYMBOL(__ip4_datagram_connect);

int ip4_datagram_connect(struct sock *sk, struct sockaddr_unsized *uaddr, int addr_len)
{
        int res;

        lock_sock(sk);
        res = __ip4_datagram_connect(sk, uaddr, addr_len);
        release_sock(sk);
        return res;
}
EXPORT_SYMBOL(ip4_datagram_connect);

/* Because UDP xmit path can manipulate sk_dst_cache without holding
 * socket lock, we need to use sk_dst_set() here,
 * even if we own the socket lock.
 */
void ip4_datagram_release_cb(struct sock *sk)
{
        const struct inet_sock *inet = inet_sk(sk);
        struct dst_entry *dst;
        struct flowi4 fl4;
        struct rtable *rt;

        rcu_read_lock();

        dst = __sk_dst_get(sk);
        if (!dst || !READ_ONCE(dst->obsolete) || dst->ops->check(dst, 0)) {
                rcu_read_unlock();
                return;
        }

        inet_sk_init_flowi4(inet, &fl4);
        rt = ip_route_output_flow(sock_net(sk), &fl4, sk);
        dst = !IS_ERR(rt) ? &rt->dst : NULL;
        sk_dst_set(sk, dst);

        rcu_read_unlock();
}
EXPORT_SYMBOL_GPL(ip4_datagram_release_cb);