1 // SPDX-License-Identifier: GPL-2.0-or-later 2 /* 3 * xfrm4_output.c - Common IPsec encapsulation code for IPv4. 4 * Copyright (c) 2004 Herbert Xu <herbert@gondor.apana.org.au> 5 */ 6 7 #include <linux/if_ether.h> 8 #include <linux/kernel.h> 9 #include <linux/module.h> 10 #include <linux/skbuff.h> 11 #include <linux/netfilter_ipv4.h> 12 #include <net/dst.h> 13 #include <net/ip.h> 14 #include <net/xfrm.h> 15 #include <net/icmp.h> 16 17 static int xfrm4_tunnel_check_size(struct sk_buff *skb) 18 { 19 int mtu, ret = 0; 20 21 if (IPCB(skb)->flags & IPSKB_XFRM_TUNNEL_SIZE) 22 goto out; 23 24 if (!(ip_hdr(skb)->frag_off & htons(IP_DF)) || skb->ignore_df) 25 goto out; 26 27 mtu = dst_mtu(skb_dst(skb)); 28 if ((!skb_is_gso(skb) && skb->len > mtu) || 29 (skb_is_gso(skb) && 30 !skb_gso_validate_network_len(skb, ip_skb_dst_mtu(skb->sk, skb)))) { 31 skb->protocol = htons(ETH_P_IP); 32 33 if (skb->sk) 34 xfrm_local_error(skb, mtu); 35 else 36 icmp_send(skb, ICMP_DEST_UNREACH, 37 ICMP_FRAG_NEEDED, htonl(mtu)); 38 ret = -EMSGSIZE; 39 } 40 out: 41 return ret; 42 } 43 44 int xfrm4_extract_output(struct xfrm_state *x, struct sk_buff *skb) 45 { 46 int err; 47 48 err = xfrm4_tunnel_check_size(skb); 49 if (err) 50 return err; 51 52 XFRM_MODE_SKB_CB(skb)->protocol = ip_hdr(skb)->protocol; 53 54 return xfrm4_extract_header(skb); 55 } 56 57 int xfrm4_output_finish(struct sock *sk, struct sk_buff *skb) 58 { 59 memset(IPCB(skb), 0, sizeof(*IPCB(skb))); 60 61 #ifdef CONFIG_NETFILTER 62 IPCB(skb)->flags |= IPSKB_XFRM_TRANSFORMED; 63 #endif 64 65 return xfrm_output(sk, skb); 66 } 67 68 static int __xfrm4_output(struct net *net, struct sock *sk, struct sk_buff *skb) 69 { 70 struct xfrm_state *x = skb_dst(skb)->xfrm; 71 const struct xfrm_state_afinfo *afinfo; 72 int ret = -EAFNOSUPPORT; 73 74 #ifdef CONFIG_NETFILTER 75 if (!x) { 76 IPCB(skb)->flags |= IPSKB_REROUTED; 77 return dst_output(net, sk, skb); 78 } 79 #endif 80 81 rcu_read_lock(); 82 afinfo = xfrm_state_afinfo_get_rcu(x->outer_mode.family); 83 if (likely(afinfo)) 84 ret = afinfo->output_finish(sk, skb); 85 else 86 kfree_skb(skb); 87 rcu_read_unlock(); 88 89 return ret; 90 } 91 92 int xfrm4_output(struct net *net, struct sock *sk, struct sk_buff *skb) 93 { 94 return NF_HOOK_COND(NFPROTO_IPV4, NF_INET_POST_ROUTING, 95 net, sk, skb, skb->dev, skb_dst(skb)->dev, 96 __xfrm4_output, 97 !(IPCB(skb)->flags & IPSKB_REROUTED)); 98 } 99 100 void xfrm4_local_error(struct sk_buff *skb, u32 mtu) 101 { 102 struct iphdr *hdr; 103 104 hdr = skb->encapsulation ? inner_ip_hdr(skb) : ip_hdr(skb); 105 ip_local_error(skb->sk, EMSGSIZE, hdr->daddr, 106 inet_sk(skb->sk)->inet_dport, mtu); 107 } 108