diff options
Diffstat (limited to 'net/ipv4/netfilter.c')
| -rw-r--r-- | net/ipv4/netfilter.c | 249 |
1 files changed, 249 insertions, 0 deletions
diff --git a/net/ipv4/netfilter.c b/net/ipv4/netfilter.c new file mode 100644 index 00000000..4f47e064 --- /dev/null +++ b/net/ipv4/netfilter.c @@ -0,0 +1,249 @@ +/* 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 <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 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 -1; + + /* Drop old route. */ + skb_dst_drop(skb); + skb_dst_set(skb, &rt->dst); + + if (skb_dst(skb)->error) + return -1; + +#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 -1; + 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 -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(skb); + if (dst->xfrm) + dst = ((struct xfrm_dst *)dst)->route; + dst_hold(dst); + + dst = xfrm_lookup(dev_net(dst->dev), dst, &fl, skb->sk, 0); + if (IS_ERR(dst)) + return -1; + + skb_dst_drop(skb); + skb_dst_set(skb, dst); + + /* 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_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; + 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 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); + +#ifdef CONFIG_SYSCTL +struct ctl_path nf_net_ipv4_netfilter_sysctl_path[] = { + { .procname = "net", }, + { .procname = "ipv4", }, + { .procname = "netfilter", }, + { } +}; +EXPORT_SYMBOL_GPL(nf_net_ipv4_netfilter_sysctl_path); +#endif /* CONFIG_SYSCTL */ |