| /* |
| * IPv4 specific functions of netfilter core |
| * |
| * Rusty Russell (C) 2000 -- This code is GPL. |
| * Patrick McHardy (C) 2006-2012 |
| */ |
| #include <linux/kernel.h> |
| #include <linux/netfilter.h> |
| #include <linux/netfilter_ipv4.h> |
| #include <linux/ip.h> |
| #include <linux/skbuff.h> |
| #include <linux/gfp.h> |
| #include <linux/export.h> |
| #include <net/route.h> |
| #include <net/xfrm.h> |
| #include <net/ip.h> |
| #include <net/netfilter/nf_queue.h> |
| |
| /* route_me_harder function, used by iptable_nat, iptable_mangle + ip_queue */ |
| int ip_route_me_harder(struct sk_buff *skb, unsigned int addr_type) |
| { |
| struct net *net = dev_net(skb_dst(skb)->dev); |
| const struct iphdr *iph = ip_hdr(skb); |
| struct rtable *rt; |
| struct flowi4 fl4 = {}; |
| __be32 saddr = iph->saddr; |
| __u8 flags = skb->sk ? inet_sk_flowi_flags(skb->sk) : 0; |
| unsigned int hh_len; |
| |
| if (addr_type == RTN_UNSPEC) |
| addr_type = inet_addr_type(net, saddr); |
| if (addr_type == RTN_LOCAL || addr_type == RTN_UNICAST) |
| flags |= FLOWI_FLAG_ANYSRC; |
| else |
| saddr = 0; |
| |
| /* some non-standard hacks like ipt_REJECT.c:send_reset() can cause |
| * packets with foreign saddr to appear on the NF_INET_LOCAL_OUT hook. |
| */ |
| fl4.daddr = iph->daddr; |
| fl4.saddr = saddr; |
| fl4.flowi4_tos = RT_TOS(iph->tos); |
| fl4.flowi4_oif = skb->sk ? skb->sk->sk_bound_dev_if : 0; |
| fl4.flowi4_mark = skb->mark; |
| fl4.flowi4_flags = flags; |
| rt = ip_route_output_key(net, &fl4); |
| if (IS_ERR(rt)) |
| return PTR_ERR(rt); |
| |
| /* Drop old route. */ |
| skb_dst_drop(skb); |
| skb_dst_set(skb, &rt->dst); |
| |
| if (skb_dst(skb)->error) |
| return skb_dst(skb)->error; |
| |
| #ifdef CONFIG_XFRM |
| if (!(IPCB(skb)->flags & IPSKB_XFRM_TRANSFORMED) && |
| xfrm_decode_session(skb, flowi4_to_flowi(&fl4), AF_INET) == 0) { |
| struct dst_entry *dst = skb_dst(skb); |
| skb_dst_set(skb, NULL); |
| dst = xfrm_lookup(net, dst, flowi4_to_flowi(&fl4), skb->sk, 0); |
| if (IS_ERR(dst)) |
| return PTR_ERR(dst); |
| skb_dst_set(skb, dst); |
| } |
| #endif |
| |
| /* Change in oif may mean change in hh_len. */ |
| hh_len = skb_dst(skb)->dev->hard_header_len; |
| if (skb_headroom(skb) < hh_len && |
| pskb_expand_head(skb, HH_DATA_ALIGN(hh_len - skb_headroom(skb)), |
| 0, GFP_ATOMIC)) |
| return -ENOMEM; |
| |
| return 0; |
| } |
| EXPORT_SYMBOL(ip_route_me_harder); |
| |
| /* |
| * 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; |
| u_int32_t mark; |
| }; |
| |
| static void nf_ip_saveroute(const struct sk_buff *skb, |
| struct nf_queue_entry *entry) |
| { |
| struct ip_rt_info *rt_info = nf_queue_entry_reroute(entry); |
| |
| if (entry->hook == NF_INET_LOCAL_OUT) { |
| const struct iphdr *iph = ip_hdr(skb); |
| |
| rt_info->tos = iph->tos; |
| rt_info->daddr = iph->daddr; |
| rt_info->saddr = iph->saddr; |
| rt_info->mark = skb->mark; |
| } |
| } |
| |
| static int nf_ip_reroute(struct sk_buff *skb, |
| const struct nf_queue_entry *entry) |
| { |
| const struct ip_rt_info *rt_info = nf_queue_entry_reroute(entry); |
| |
| if (entry->hook == NF_INET_LOCAL_OUT) { |
| const struct iphdr *iph = ip_hdr(skb); |
| |
| if (!(iph->tos == rt_info->tos && |
| skb->mark == rt_info->mark && |
| 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_INET_PRE_ROUTING && hook != NF_INET_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 __sum16 nf_ip_checksum_partial(struct sk_buff *skb, unsigned int hook, |
| unsigned int dataoff, unsigned int len, |
| u_int8_t protocol) |
| { |
| const struct iphdr *iph = ip_hdr(skb); |
| __sum16 csum = 0; |
| |
| switch (skb->ip_summed) { |
| case CHECKSUM_COMPLETE: |
| if (len == skb->len - dataoff) |
| return nf_ip_checksum(skb, hook, dataoff, protocol); |
| /* fall through */ |
| case CHECKSUM_NONE: |
| skb->csum = csum_tcpudp_nofold(iph->saddr, iph->daddr, protocol, |
| skb->len - dataoff, 0); |
| skb->ip_summed = CHECKSUM_NONE; |
| return __skb_checksum_complete_head(skb, dataoff + len); |
| } |
| return csum; |
| } |
| |
| static int nf_ip_route(struct net *net, struct dst_entry **dst, |
| struct flowi *fl, bool strict __always_unused) |
| { |
| struct rtable *rt = ip_route_output_key(net, &fl->u.ip4); |
| if (IS_ERR(rt)) |
| return PTR_ERR(rt); |
| *dst = &rt->dst; |
| return 0; |
| } |
| |
| static const struct nf_afinfo nf_ip_afinfo = { |
| .family = AF_INET, |
| .checksum = nf_ip_checksum, |
| .checksum_partial = nf_ip_checksum_partial, |
| .route = nf_ip_route, |
| .saveroute = nf_ip_saveroute, |
| .reroute = nf_ip_reroute, |
| .route_key_size = sizeof(struct ip_rt_info), |
| }; |
| |
| static int __init ipv4_netfilter_init(void) |
| { |
| return nf_register_afinfo(&nf_ip_afinfo); |
| } |
| |
| static void __exit ipv4_netfilter_fini(void) |
| { |
| nf_unregister_afinfo(&nf_ip_afinfo); |
| } |
| |
| module_init(ipv4_netfilter_init); |
| module_exit(ipv4_netfilter_fini); |