1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 * xfrm6_output.c - Common IPsec encapsulation code for IPv6.
4 * Copyright (C) 2002 USAGI/WIDE Project
5 * Copyright (c) 2004 Herbert Xu <herbert@gondor.apana.org.au>
6 */
7
8#include <linux/if_ether.h>
9#include <linux/kernel.h>
10#include <linux/module.h>
11#include <linux/skbuff.h>
12#include <linux/icmpv6.h>
13#include <linux/netfilter_ipv6.h>
14#include <net/dst.h>
15#include <net/ipv6.h>
16#include <net/ip6_route.h>
17#include <net/xfrm.h>
18
19void xfrm6_local_rxpmtu(struct sk_buff *skb, u32 mtu)
20{
21	struct flowi6 fl6;
22	struct sock *sk = skb->sk;
23
24	fl6.flowi6_oif = sk->sk_bound_dev_if;
25	fl6.daddr = ipv6_hdr(skb)->daddr;
26
27	ipv6_local_rxpmtu(sk, &fl6, mtu);
28}
29
30void xfrm6_local_error(struct sk_buff *skb, u32 mtu)
31{
32	struct flowi6 fl6;
33	const struct ipv6hdr *hdr;
34	struct sock *sk = skb->sk;
35
36	hdr = skb->encapsulation ? inner_ipv6_hdr(skb) : ipv6_hdr(skb);
37	fl6.fl6_dport = inet_sk(sk)->inet_dport;
38	fl6.daddr = hdr->daddr;
39
40	ipv6_local_error(sk, EMSGSIZE, &fl6, mtu);
41}
42
43static int __xfrm6_output_finish(struct net *net, struct sock *sk, struct sk_buff *skb)
44{
45	return xfrm_output(sk, skb);
46}
47
48static int xfrm6_noneed_fragment(struct sk_buff *skb)
49{
50	struct frag_hdr *fh;
51	u8 prevhdr = ipv6_hdr(skb)->nexthdr;
52
53	if (prevhdr != NEXTHDR_FRAGMENT)
54		return 0;
55	fh = (struct frag_hdr *)(skb->data + sizeof(struct ipv6hdr));
56	if (fh->nexthdr == NEXTHDR_ESP || fh->nexthdr == NEXTHDR_AUTH)
57		return 1;
58	return 0;
59}
60
61static int __xfrm6_output(struct net *net, struct sock *sk, struct sk_buff *skb)
62{
63	struct dst_entry *dst = skb_dst(skb);
64	struct xfrm_state *x = dst->xfrm;
65	unsigned int mtu;
66	bool toobig;
67
68#ifdef CONFIG_NETFILTER
69	if (!x) {
70		IP6CB(skb)->flags |= IP6SKB_REROUTED;
71		return dst_output(net, sk, skb);
72	}
73#endif
74
75	if (x->props.mode != XFRM_MODE_TUNNEL)
76		goto skip_frag;
77
78	if (skb->protocol == htons(ETH_P_IPV6))
79		mtu = ip6_skb_dst_mtu(skb);
80	else
81		mtu = dst_mtu(skb_dst(skb));
82
83	toobig = skb->len > mtu && !skb_is_gso(skb);
84
85	if (toobig && xfrm6_local_dontfrag(skb->sk)) {
86		xfrm6_local_rxpmtu(skb, mtu);
87		kfree_skb(skb);
88		return -EMSGSIZE;
89	} else if (toobig && xfrm6_noneed_fragment(skb)) {
90		skb->ignore_df = 1;
91		goto skip_frag;
92	} else if (!skb->ignore_df && toobig && skb->sk) {
93		xfrm_local_error(skb, mtu);
94		kfree_skb(skb);
95		return -EMSGSIZE;
96	}
97
98	if (toobig)
99		return ip6_fragment(net, sk, skb,
100				    __xfrm6_output_finish);
101
102skip_frag:
103	return xfrm_output(sk, skb);
104}
105
106int xfrm6_output(struct net *net, struct sock *sk, struct sk_buff *skb)
107{
108	return NF_HOOK_COND(NFPROTO_IPV6, NF_INET_POST_ROUTING,
109			    net, sk, skb,  skb->dev, skb_dst(skb)->dev,
110			    __xfrm6_output,
111			    !(IP6CB(skb)->flags & IP6SKB_REROUTED));
112}
113