/* * xfrm4_output.c - Common IPsec encapsulation code for IPv4. * Copyright (c) 2004 Herbert Xu <herbert@gondor.apana.org.au> * * This program is free software; you can redistribute it and/or * modify it under the terms of the GNU General Public License * as published by the Free Software Foundation; either version * 2 of the License, or (at your option) any later version. */ #include <linux/compiler.h> #include <linux/skbuff.h> #include <linux/spinlock.h> #include <linux/netfilter_ipv4.h> #include <net/inet_ecn.h> #include <net/ip.h> #include <net/xfrm.h> #include <net/icmp.h> /* Add encapsulation header. * * In transport mode, the IP header will be moved forward to make space * for the encapsulation header. * * In tunnel mode, the top IP header will be constructed per RFC 2401. * The following fields in it shall be filled in by x->type->output: * tot_len * check * * On exit, skb->h will be set to the start of the payload to be processed * by x->type->output and skb->nh will be set to the top IP header. */ static void xfrm4_encap(struct sk_buff *skb) { struct dst_entry *dst = skb->dst; struct xfrm_state *x = dst->xfrm; struct iphdr *iph, *top_iph; int flags; iph = skb->nh.iph; skb->h.ipiph = iph; skb->nh.raw = skb_push(skb, x->props.header_len); top_iph = skb->nh.iph; if (!x->props.mode) { skb->h.raw += iph->ihl*4; memmove(top_iph, iph, iph->ihl*4); return; } top_iph->ihl = 5; top_iph->version = 4; /* DS disclosed */ top_iph->tos = INET_ECN_encapsulate(iph->tos, iph->tos); flags = x->props.flags; if (flags & XFRM_STATE_NOECN) IP_ECN_clear(top_iph); top_iph->frag_off = (flags & XFRM_STATE_NOPMTUDISC) ? 0 : (iph->frag_off & htons(IP_DF)); if (!top_iph->frag_off) __ip_select_ident(top_iph, dst, 0); top_iph->ttl = dst_metric(dst->child, RTAX_HOPLIMIT); top_iph->saddr = x->props.saddr.a4; top_iph->daddr = x->id.daddr.a4; top_iph->protocol = IPPROTO_IPIP; memset(&(IPCB(skb)->opt), 0, sizeof(struct ip_options)); } static int xfrm4_tunnel_check_size(struct sk_buff *skb) { int mtu, ret = 0; struct dst_entry *dst; struct iphdr *iph = skb->nh.iph; if (IPCB(skb)->flags & IPSKB_XFRM_TUNNEL_SIZE) goto out; IPCB(skb)->flags |= IPSKB_XFRM_TUNNEL_SIZE; if (!(iph->frag_off & htons(IP_DF)) || skb->local_df) goto out; dst = skb->dst; mtu = dst_mtu(dst); if (skb->len > mtu) { icmp_send(skb, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED, htonl(mtu)); ret = -EMSGSIZE; } out: return ret; } static int xfrm4_output_one(struct sk_buff *skb) { struct dst_entry *dst = skb->dst; struct xfrm_state *x = dst->xfrm; int err; if (skb->ip_summed == CHECKSUM_HW) { err = skb_checksum_help(skb, 0); if (err) goto error_nolock; } if (x->props.mode) { err = xfrm4_tunnel_check_size(skb); if (err) goto error_nolock; } do { spin_lock_bh(&x->lock); err = xfrm_state_check(x, skb); if (err) goto error; xfrm4_encap(skb); err = x->type->output(x, skb); if (err) goto error; x->curlft.bytes += skb->len; x->curlft.packets++; spin_unlock_bh(&x->lock); if (!(skb->dst = dst_pop(dst))) { err = -EHOSTUNREACH; goto error_nolock; } dst = skb->dst; x = dst->xfrm; } while (x && !x->props.mode); IPCB(skb)->flags |= IPSKB_XFRM_TRANSFORMED; err = 0; out_exit: return err; error: spin_unlock_bh(&x->lock); error_nolock: kfree_skb(skb); goto out_exit; } static int xfrm4_output_finish(struct sk_buff *skb) { int err; #ifdef CONFIG_NETFILTER if (!skb->dst->xfrm) { IPCB(skb)->flags |= IPSKB_REROUTED; return dst_output(skb); } #endif while (likely((err = xfrm4_output_one(skb)) == 0)) { nf_reset(skb); err = nf_hook(PF_INET, NF_IP_LOCAL_OUT, &skb, NULL, skb->dst->dev, dst_output); if (unlikely(err != 1)) break; if (!skb->dst->xfrm) return dst_output(skb); err = nf_hook(PF_INET, NF_IP_POST_ROUTING, &skb, NULL, skb->dst->dev, xfrm4_output_finish); if (unlikely(err != 1)) break; } return err; } int xfrm4_output(struct sk_buff *skb) { return NF_HOOK_COND(PF_INET, NF_IP_POST_ROUTING, skb, NULL, skb->dst->dev, xfrm4_output_finish, !(IPCB(skb)->flags & IPSKB_REROUTED)); }