net/ipv6/xfrm6_output.c

   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
  19 void 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
  30 void 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
  43 static int __xfrm6_output_finish(struct net *net, struct sock *sk, struct sk_buff *skb)
  44 {
  45         return xfrm_output(sk, skb);
  46 }
  47
  48 static 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
  61 static 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
 102 skip_frag:
 103         return xfrm_output(sk, skb);
 104 }
 105
 106 int 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 }