// 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.
 *
 *             Support for INET6 connection oriented protocols.
 *
 * Authors:    See the TCPv6 sources
 */

#include <linux/module.h>
#include <linux/in6.h>
#include <linux/ipv6.h>
#include <linux/jhash.h>
#include <linux/slab.h>

#include <net/addrconf.h>
#include <net/inet_connection_sock.h>
#include <net/inet_ecn.h>
#include <net/inet_hashtables.h>
#include <net/ip6_route.h>
#include <net/sock.h>
#include <net/inet6_connection_sock.h>
#include <net/sock_reuseport.h>

struct dst_entry *inet6_csk_route_req(const struct sock *sk,
                                      struct dst_entry *dst,
                                      struct flowi6 *fl6,
                                      const struct request_sock *req,
                                      u8 proto)
{
        const struct inet_request_sock *ireq = inet_rsk(req);
        const struct ipv6_pinfo *np = inet6_sk(sk);
        struct in6_addr *final_p, final;

        memset(fl6, 0, sizeof(*fl6));
        fl6->flowi6_proto = proto;
        fl6->daddr = ireq->ir_v6_rmt_addr;
        rcu_read_lock();
        final_p = fl6_update_dst(fl6, rcu_dereference(np->opt), &final);
        rcu_read_unlock();
        fl6->saddr = ireq->ir_v6_loc_addr;
        fl6->flowi6_oif = ireq->ir_iif;
        fl6->flowi6_mark = ireq->ir_mark;
        fl6->fl6_dport = ireq->ir_rmt_port;
        fl6->fl6_sport = htons(ireq->ir_num);
        fl6->flowi6_uid = sk_uid(sk);
        security_req_classify_flow(req, flowi6_to_flowi_common(fl6));

        if (!dst) {
                dst = ip6_dst_lookup_flow(sock_net(sk), sk, fl6, final_p);
                if (IS_ERR(dst))
                        return NULL;
        }
        return dst;
}

static struct dst_entry *inet6_csk_route_socket(struct sock *sk,
                                                struct flowi6 *fl6)
{
        struct inet_sock *inet = inet_sk(sk);
        struct ipv6_pinfo *np = inet6_sk(sk);
        struct in6_addr *final_p;
        struct dst_entry *dst;

        memset(fl6, 0, sizeof(*fl6));
        fl6->flowi6_proto = sk->sk_protocol;
        fl6->daddr = sk->sk_v6_daddr;
        fl6->saddr = np->saddr;
        fl6->flowlabel = np->flow_label;
        IP6_ECN_flow_xmit(sk, fl6->flowlabel);
        fl6->flowi6_oif = sk->sk_bound_dev_if;
        fl6->flowi6_mark = sk->sk_mark;
        fl6->fl6_sport = inet->inet_sport;
        fl6->fl6_dport = inet->inet_dport;
        fl6->flowi6_uid = sk_uid(sk);
        security_sk_classify_flow(sk, flowi6_to_flowi_common(fl6));

        rcu_read_lock();
        final_p = fl6_update_dst(fl6, rcu_dereference(np->opt), &np->final);
        rcu_read_unlock();

        dst = ip6_dst_lookup_flow(sock_net(sk), sk, fl6, final_p);

        if (!IS_ERR(dst))
                ip6_dst_store(sk, dst, false, false);

        return dst;
}

int inet6_csk_xmit(struct sock *sk, struct sk_buff *skb, struct flowi *fl_unused)
{
        struct flowi6 *fl6 = &inet_sk(sk)->cork.fl.u.ip6;
        struct ipv6_pinfo *np = inet6_sk(sk);
        struct dst_entry *dst;
        int res;

        dst = __sk_dst_check(sk, np->dst_cookie);
        if (unlikely(!dst)) {
                dst = inet6_csk_route_socket(sk, fl6);
                if (IS_ERR(dst)) {
                        WRITE_ONCE(sk->sk_err_soft, -PTR_ERR(dst));
                        sk->sk_route_caps = 0;
                        kfree_skb(skb);
                        return PTR_ERR(dst);
                }
                /* Restore final destination back after routing done */
                fl6->daddr = sk->sk_v6_daddr;
        }

        rcu_read_lock();
        skb_dst_set_noref(skb, dst);

        res = ip6_xmit(sk, skb, fl6, sk->sk_mark, rcu_dereference(np->opt),
                       np->tclass, READ_ONCE(sk->sk_priority));
        rcu_read_unlock();
        return res;
}
EXPORT_SYMBOL_GPL(inet6_csk_xmit);

struct dst_entry *inet6_csk_update_pmtu(struct sock *sk, u32 mtu)
{
        struct flowi6 *fl6 = &inet_sk(sk)->cork.fl.u.ip6;
        struct dst_entry *dst;

        dst = inet6_csk_route_socket(sk, fl6);

        if (IS_ERR(dst))
                return NULL;
        dst->ops->update_pmtu(dst, sk, NULL, mtu, true);

        dst = inet6_csk_route_socket(sk, fl6);
        return IS_ERR(dst) ? NULL : dst;
}