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

	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));

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

	return dst;
}

static inline
struct dst_entry *__inet6_csk_dst_check(struct sock *sk, u32 cookie)
{
	return __sk_dst_check(sk, cookie);
}

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, final;
	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), &final);
	rcu_read_unlock();

	dst = __inet6_csk_dst_check(sk, np->dst_cookie);
	if (!dst) {
		dst = ip6_dst_lookup_flow(sock_net(sk), sk, fl6, final_p);

		if (!IS_ERR(dst))
			ip6_dst_store(sk, dst, NULL, NULL);
	}
	return dst;
}

int inet6_csk_xmit(struct sock *sk, struct sk_buff *skb, struct flowi *fl_unused)
{
	struct ipv6_pinfo *np = inet6_sk(sk);
	struct flowi6 fl6;
	struct dst_entry *dst;
	int res;

	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);
	}

	rcu_read_lock();
	skb_dst_set_noref(skb, dst);

	/* Restore final destination back after routing done */
	fl6.daddr = sk->sk_v6_daddr;

	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;
	struct dst_entry *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;
}