/* IPv4 specific functions of netfilter core */ #include <linux/kernel.h> #include <linux/netfilter.h> #include <linux/netfilter_ipv4.h> #include <linux/ip.h> #include <linux/skbuff.h> #include <net/route.h> #include <net/xfrm.h> #include <net/ip.h> /* route_me_harder function, used by iptable_nat, iptable_mangle + ip_queue */ int ip_route_me_harder(struct sk_buff *skb, unsigned addr_type) { const struct iphdr *iph = ip_hdr(skb); struct rtable *rt; struct flowi fl = {}; struct dst_entry *odst; unsigned int hh_len; unsigned int type; type = inet_addr_type(iph->saddr); if (addr_type == RTN_UNSPEC) addr_type = type; /* some non-standard hacks like ipt_REJECT.c:send_reset() can cause * packets with foreign saddr to appear on the NF_IP_LOCAL_OUT hook. */ if (addr_type == RTN_LOCAL) { fl.nl_u.ip4_u.daddr = iph->daddr; if (type == RTN_LOCAL) fl.nl_u.ip4_u.saddr = iph->saddr; fl.nl_u.ip4_u.tos = RT_TOS(iph->tos); fl.oif = skb->sk ? skb->sk->sk_bound_dev_if : 0; fl.mark = skb->mark; if (ip_route_output_key(&rt, &fl) != 0) return -1; /* Drop old route. */ dst_release(skb->dst); skb->dst = &rt->u.dst; } else { /* non-local src, find valid iif to satisfy * rp-filter when calling ip_route_input. */ fl.nl_u.ip4_u.daddr = iph->saddr; if (ip_route_output_key(&rt, &fl) != 0) return -1; odst = skb->dst; if (ip_route_input(skb, iph->daddr, iph->saddr, RT_TOS(iph->tos), rt->u.dst.dev) != 0) { dst_release(&rt->u.dst); return -1; } dst_release(&rt->u.dst); dst_release(odst); } if (skb->dst->error) return -1; #ifdef CONFIG_XFRM if (!(IPCB(skb)->flags & IPSKB_XFRM_TRANSFORMED) && xfrm_decode_session(skb, &fl, AF_INET) == 0) if (xfrm_lookup(&skb->dst, &fl, skb->sk, 0)) return -1; #endif /* Change in oif may mean change in hh_len. */ hh_len = skb->dst->dev->hard_header_len; if (skb_headroom(skb) < hh_len && pskb_expand_head(skb, hh_len - skb_headroom(skb), 0, GFP_ATOMIC)) return -1; return 0; } EXPORT_SYMBOL(ip_route_me_harder); #ifdef CONFIG_XFRM int ip_xfrm_me_harder(struct sk_buff *skb) { struct flowi fl; unsigned int hh_len; struct dst_entry *dst; if (IPCB(skb)->flags & IPSKB_XFRM_TRANSFORMED) return 0; if (xfrm_decode_session(skb, &fl, AF_INET) < 0) return -1; dst = skb->dst; if (dst->xfrm) dst = ((struct xfrm_dst *)dst)->route; dst_hold(dst); if (xfrm_lookup(&dst, &fl, skb->sk, 0) < 0) return -1; dst_release(skb->dst); skb->dst = dst; /* Change in oif may mean change in hh_len. */ hh_len = skb->dst->dev->hard_header_len; if (skb_headroom(skb) < hh_len && pskb_expand_head(skb, hh_len - skb_headroom(skb), 0, GFP_ATOMIC)) return -1; return 0; } EXPORT_SYMBOL(ip_xfrm_me_harder); #endif void (*ip_nat_decode_session)(struct sk_buff *, struct flowi *); EXPORT_SYMBOL(ip_nat_decode_session); /* * Extra routing may needed on local out, as the QUEUE target never * returns control to the table. */ struct ip_rt_info { __be32 daddr; __be32 saddr; u_int8_t tos; }; static void nf_ip_saveroute(const struct sk_buff *skb, struct nf_info *info) { struct ip_rt_info *rt_info = nf_info_reroute(info); if (info->hook == NF_IP_LOCAL_OUT) { const struct iphdr *iph = ip_hdr(skb); rt_info->tos = iph->tos; rt_info->daddr = iph->daddr; rt_info->saddr = iph->saddr; } } static int nf_ip_reroute(struct sk_buff *skb, const struct nf_info *info) { const struct ip_rt_info *rt_info = nf_info_reroute(info); if (info->hook == NF_IP_LOCAL_OUT) { const struct iphdr *iph = ip_hdr(skb); if (!(iph->tos == rt_info->tos && iph->daddr == rt_info->daddr && iph->saddr == rt_info->saddr)) return ip_route_me_harder(skb, RTN_UNSPEC); } return 0; } __sum16 nf_ip_checksum(struct sk_buff *skb, unsigned int hook, unsigned int dataoff, u_int8_t protocol) { const struct iphdr *iph = ip_hdr(skb); __sum16 csum = 0; switch (skb->ip_summed) { case CHECKSUM_COMPLETE: if (hook != NF_IP_PRE_ROUTING && hook != NF_IP_LOCAL_IN) break; if ((protocol == 0 && !csum_fold(skb->csum)) || !csum_tcpudp_magic(iph->saddr, iph->daddr, skb->len - dataoff, protocol, skb->csum)) { skb->ip_summed = CHECKSUM_UNNECESSARY; break; } /* fall through */ case CHECKSUM_NONE: if (protocol == 0) skb->csum = 0; else skb->csum = csum_tcpudp_nofold(iph->saddr, iph->daddr, skb->len - dataoff, protocol, 0); csum = __skb_checksum_complete(skb); } return csum; } EXPORT_SYMBOL(nf_ip_checksum); static struct nf_afinfo nf_ip_afinfo = { .family = AF_INET, .checksum = nf_ip_checksum, .saveroute = nf_ip_saveroute, .reroute = nf_ip_reroute, .route_key_size = sizeof(struct ip_rt_info), }; static int ipv4_netfilter_init(void) { return nf_register_afinfo(&nf_ip_afinfo); } static void ipv4_netfilter_fini(void) { nf_unregister_afinfo(&nf_ip_afinfo); } module_init(ipv4_netfilter_init); module_exit(ipv4_netfilter_fini);