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 int xfrm6_find_1stfragopt(struct xfrm_state *x, struct sk_buff *skb,
  20                           u8 **prevhdr)
  21 {
  22         return ip6_find_1stfragopt(skb, prevhdr);
  23 }
  24 EXPORT_SYMBOL(xfrm6_find_1stfragopt);
  25
  26 static int xfrm6_local_dontfrag(struct sk_buff *skb)
  27 {
  28         int proto;
  29         struct sock *sk = skb->sk;
  30
  31         if (sk) {
  32                 if (sk->sk_family != AF_INET6)
  33                         return 0;
  34
  35                 proto = sk->sk_protocol;
  36                 if (proto == IPPROTO_UDP || proto == IPPROTO_RAW)
  37                         return inet6_sk(sk)->dontfrag;
  38         }
  39
  40         return 0;
  41 }
  42
  43 static void xfrm6_local_rxpmtu(struct sk_buff *skb, u32 mtu)
  44 {
  45         struct flowi6 fl6;
  46         struct sock *sk = skb->sk;
  47
  48         fl6.flowi6_oif = sk->sk_bound_dev_if;
  49         fl6.daddr = ipv6_hdr(skb)->daddr;
  50
  51         ipv6_local_rxpmtu(sk, &fl6, mtu);
  52 }
  53
  54 void xfrm6_local_error(struct sk_buff *skb, u32 mtu)
  55 {
  56         struct flowi6 fl6;
  57         const struct ipv6hdr *hdr;
  58         struct sock *sk = skb->sk;
  59
  60         hdr = skb->encapsulation ? inner_ipv6_hdr(skb) : ipv6_hdr(skb);
  61         fl6.fl6_dport = inet_sk(sk)->inet_dport;
  62         fl6.daddr = hdr->daddr;
  63
  64         ipv6_local_error(sk, EMSGSIZE, &fl6, mtu);
  65 }
  66
  67 static int xfrm6_tunnel_check_size(struct sk_buff *skb)
  68 {
  69         int mtu, ret = 0;
  70         struct dst_entry *dst = skb_dst(skb);
  71
  72         if (skb->ignore_df)
  73                 goto out;
  74
  75         mtu = dst_mtu(dst);
  76         if (mtu < IPV6_MIN_MTU)
  77                 mtu = IPV6_MIN_MTU;
  78
  79         if ((!skb_is_gso(skb) && skb->len > mtu) ||
  80             (skb_is_gso(skb) &&
  81              !skb_gso_validate_network_len(skb, ip6_skb_dst_mtu(skb)))) {
  82                 skb->dev = dst->dev;
  83                 skb->protocol = htons(ETH_P_IPV6);
  84
  85                 if (xfrm6_local_dontfrag(skb))
  86                         xfrm6_local_rxpmtu(skb, mtu);
  87                 else if (skb->sk)
  88                         xfrm_local_error(skb, mtu);
  89                 else
  90                         icmpv6_send(skb, ICMPV6_PKT_TOOBIG, 0, mtu);
  91                 ret = -EMSGSIZE;
  92         }
  93 out:
  94         return ret;
  95 }
  96
  97 int xfrm6_extract_output(struct xfrm_state *x, struct sk_buff *skb)
  98 {
  99         int err;
 100
 101         err = xfrm6_tunnel_check_size(skb);
 102         if (err)
 103                 return err;
 104
 105         XFRM_MODE_SKB_CB(skb)->protocol = ipv6_hdr(skb)->nexthdr;
 106
 107         return xfrm6_extract_header(skb);
 108 }
 109
 110 int xfrm6_output_finish(struct sock *sk, struct sk_buff *skb)
 111 {
 112         memset(IP6CB(skb), 0, sizeof(*IP6CB(skb)));
 113
 114         IP6CB(skb)->flags |= IP6SKB_XFRM_TRANSFORMED;
 115
 116         return xfrm_output(sk, skb);
 117 }
 118
 119 static int __xfrm6_output_state_finish(struct xfrm_state *x, struct sock *sk,
 120                                        struct sk_buff *skb)
 121 {
 122         const struct xfrm_state_afinfo *afinfo;
 123         int ret = -EAFNOSUPPORT;
 124
 125         rcu_read_lock();
 126         afinfo = xfrm_state_afinfo_get_rcu(x->outer_mode.family);
 127         if (likely(afinfo))
 128                 ret = afinfo->output_finish(sk, skb);
 129         else
 130                 kfree_skb(skb);
 131         rcu_read_unlock();
 132
 133         return ret;
 134 }
 135
 136 static int __xfrm6_output_finish(struct net *net, struct sock *sk, struct sk_buff *skb)
 137 {
 138         struct xfrm_state *x = skb_dst(skb)->xfrm;
 139
 140         return __xfrm6_output_state_finish(x, sk, skb);
 141 }
 142
 143 static int __xfrm6_output(struct net *net, struct sock *sk, struct sk_buff *skb)
 144 {
 145         struct dst_entry *dst = skb_dst(skb);
 146         struct xfrm_state *x = dst->xfrm;
 147         int mtu;
 148         bool toobig;
 149
 150 #ifdef CONFIG_NETFILTER
 151         if (!x) {
 152                 IP6CB(skb)->flags |= IP6SKB_REROUTED;
 153                 return dst_output(net, sk, skb);
 154         }
 155 #endif
 156
 157         if (x->props.mode != XFRM_MODE_TUNNEL)
 158                 goto skip_frag;
 159
 160         if (skb->protocol == htons(ETH_P_IPV6))
 161                 mtu = ip6_skb_dst_mtu(skb);
 162         else
 163                 mtu = dst_mtu(skb_dst(skb));
 164
 165         toobig = skb->len > mtu && !skb_is_gso(skb);
 166
 167         if (toobig && xfrm6_local_dontfrag(skb)) {
 168                 xfrm6_local_rxpmtu(skb, mtu);
 169                 kfree_skb(skb);
 170                 return -EMSGSIZE;
 171         } else if (!skb->ignore_df && toobig && skb->sk) {
 172                 xfrm_local_error(skb, mtu);
 173                 kfree_skb(skb);
 174                 return -EMSGSIZE;
 175         }
 176
 177         if (toobig || dst_allfrag(skb_dst(skb)))
 178                 return ip6_fragment(net, sk, skb,
 179                                     __xfrm6_output_finish);
 180
 181 skip_frag:
 182         return __xfrm6_output_state_finish(x, sk, skb);
 183 }
 184
 185 int xfrm6_output(struct net *net, struct sock *sk, struct sk_buff *skb)
 186 {
 187         return NF_HOOK_COND(NFPROTO_IPV6, NF_INET_POST_ROUTING,
 188                             net, sk, skb,  skb->dev, skb_dst(skb)->dev,
 189                             __xfrm6_output,
 190                             !(IP6CB(skb)->flags & IP6SKB_REROUTED));
 191 }