| #include <linux/kernel.h> |
| #include <linux/init.h> |
| #include <linux/module.h> |
| #include <linux/netfilter.h> |
| #include <linux/rhashtable.h> |
| #include <linux/ip.h> |
| #include <linux/netdevice.h> |
| #include <net/ip.h> |
| #include <net/neighbour.h> |
| #include <net/netfilter/nf_flow_table.h> |
| #include <net/netfilter/nf_tables.h> |
| /* For layer 4 checksum field offset. */ |
| #include <linux/tcp.h> |
| #include <linux/udp.h> |
| |
| static int nf_flow_nat_ip_tcp(struct sk_buff *skb, unsigned int thoff, |
| __be32 addr, __be32 new_addr) |
| { |
| struct tcphdr *tcph; |
| |
| if (!pskb_may_pull(skb, thoff + sizeof(*tcph)) || |
| skb_try_make_writable(skb, thoff + sizeof(*tcph))) |
| return -1; |
| |
| tcph = (void *)(skb_network_header(skb) + thoff); |
| inet_proto_csum_replace4(&tcph->check, skb, addr, new_addr, true); |
| |
| return 0; |
| } |
| |
| static int nf_flow_nat_ip_udp(struct sk_buff *skb, unsigned int thoff, |
| __be32 addr, __be32 new_addr) |
| { |
| struct udphdr *udph; |
| |
| if (!pskb_may_pull(skb, thoff + sizeof(*udph)) || |
| skb_try_make_writable(skb, thoff + sizeof(*udph))) |
| return -1; |
| |
| udph = (void *)(skb_network_header(skb) + thoff); |
| if (udph->check || skb->ip_summed == CHECKSUM_PARTIAL) { |
| inet_proto_csum_replace4(&udph->check, skb, addr, |
| new_addr, true); |
| if (!udph->check) |
| udph->check = CSUM_MANGLED_0; |
| } |
| |
| return 0; |
| } |
| |
| static int nf_flow_nat_ip_l4proto(struct sk_buff *skb, struct iphdr *iph, |
| unsigned int thoff, __be32 addr, |
| __be32 new_addr) |
| { |
| switch (iph->protocol) { |
| case IPPROTO_TCP: |
| if (nf_flow_nat_ip_tcp(skb, thoff, addr, new_addr) < 0) |
| return NF_DROP; |
| break; |
| case IPPROTO_UDP: |
| if (nf_flow_nat_ip_udp(skb, thoff, addr, new_addr) < 0) |
| return NF_DROP; |
| break; |
| } |
| |
| return 0; |
| } |
| |
| static int nf_flow_snat_ip(const struct flow_offload *flow, struct sk_buff *skb, |
| struct iphdr *iph, unsigned int thoff, |
| enum flow_offload_tuple_dir dir) |
| { |
| __be32 addr, new_addr; |
| |
| switch (dir) { |
| case FLOW_OFFLOAD_DIR_ORIGINAL: |
| addr = iph->saddr; |
| new_addr = flow->tuplehash[FLOW_OFFLOAD_DIR_REPLY].tuple.dst_v4.s_addr; |
| iph->saddr = new_addr; |
| break; |
| case FLOW_OFFLOAD_DIR_REPLY: |
| addr = iph->daddr; |
| new_addr = flow->tuplehash[FLOW_OFFLOAD_DIR_ORIGINAL].tuple.src_v4.s_addr; |
| iph->daddr = new_addr; |
| break; |
| default: |
| return -1; |
| } |
| csum_replace4(&iph->check, addr, new_addr); |
| |
| return nf_flow_nat_ip_l4proto(skb, iph, thoff, addr, new_addr); |
| } |
| |
| static int nf_flow_dnat_ip(const struct flow_offload *flow, struct sk_buff *skb, |
| struct iphdr *iph, unsigned int thoff, |
| enum flow_offload_tuple_dir dir) |
| { |
| __be32 addr, new_addr; |
| |
| switch (dir) { |
| case FLOW_OFFLOAD_DIR_ORIGINAL: |
| addr = iph->daddr; |
| new_addr = flow->tuplehash[FLOW_OFFLOAD_DIR_REPLY].tuple.src_v4.s_addr; |
| iph->daddr = new_addr; |
| break; |
| case FLOW_OFFLOAD_DIR_REPLY: |
| addr = iph->saddr; |
| new_addr = flow->tuplehash[FLOW_OFFLOAD_DIR_ORIGINAL].tuple.dst_v4.s_addr; |
| iph->saddr = new_addr; |
| break; |
| default: |
| return -1; |
| } |
| |
| return nf_flow_nat_ip_l4proto(skb, iph, thoff, addr, new_addr); |
| } |
| |
| static int nf_flow_nat_ip(const struct flow_offload *flow, struct sk_buff *skb, |
| enum flow_offload_tuple_dir dir) |
| { |
| struct iphdr *iph = ip_hdr(skb); |
| unsigned int thoff = iph->ihl * 4; |
| |
| if (flow->flags & FLOW_OFFLOAD_SNAT && |
| (nf_flow_snat_port(flow, skb, thoff, iph->protocol, dir) < 0 || |
| nf_flow_snat_ip(flow, skb, iph, thoff, dir) < 0)) |
| return -1; |
| if (flow->flags & FLOW_OFFLOAD_DNAT && |
| (nf_flow_dnat_port(flow, skb, thoff, iph->protocol, dir) < 0 || |
| nf_flow_dnat_ip(flow, skb, iph, thoff, dir) < 0)) |
| return -1; |
| |
| return 0; |
| } |
| |
| static bool ip_has_options(unsigned int thoff) |
| { |
| return thoff != sizeof(struct iphdr); |
| } |
| |
| static int nf_flow_tuple_ip(struct sk_buff *skb, const struct net_device *dev, |
| struct flow_offload_tuple *tuple) |
| { |
| struct flow_ports *ports; |
| unsigned int thoff; |
| struct iphdr *iph; |
| |
| if (!pskb_may_pull(skb, sizeof(*iph))) |
| return -1; |
| |
| iph = ip_hdr(skb); |
| thoff = iph->ihl * 4; |
| |
| if (ip_is_fragment(iph) || |
| unlikely(ip_has_options(thoff))) |
| return -1; |
| |
| if (iph->protocol != IPPROTO_TCP && |
| iph->protocol != IPPROTO_UDP) |
| return -1; |
| |
| thoff = iph->ihl * 4; |
| if (!pskb_may_pull(skb, thoff + sizeof(*ports))) |
| return -1; |
| |
| ports = (struct flow_ports *)(skb_network_header(skb) + thoff); |
| |
| tuple->src_v4.s_addr = iph->saddr; |
| tuple->dst_v4.s_addr = iph->daddr; |
| tuple->src_port = ports->source; |
| tuple->dst_port = ports->dest; |
| tuple->l3proto = AF_INET; |
| tuple->l4proto = iph->protocol; |
| tuple->iifidx = dev->ifindex; |
| |
| return 0; |
| } |
| |
| /* Based on ip_exceeds_mtu(). */ |
| static bool __nf_flow_exceeds_mtu(const struct sk_buff *skb, unsigned int mtu) |
| { |
| if (skb->len <= mtu) |
| return false; |
| |
| if ((ip_hdr(skb)->frag_off & htons(IP_DF)) == 0) |
| return false; |
| |
| if (skb_is_gso(skb) && skb_gso_validate_mtu(skb, mtu)) |
| return false; |
| |
| return true; |
| } |
| |
| static bool nf_flow_exceeds_mtu(struct sk_buff *skb, const struct rtable *rt) |
| { |
| u32 mtu; |
| |
| mtu = ip_dst_mtu_maybe_forward(&rt->dst, true); |
| if (__nf_flow_exceeds_mtu(skb, mtu)) |
| return true; |
| |
| return false; |
| } |
| |
| unsigned int |
| nf_flow_offload_ip_hook(void *priv, struct sk_buff *skb, |
| const struct nf_hook_state *state) |
| { |
| struct flow_offload_tuple_rhash *tuplehash; |
| struct nf_flowtable *flow_table = priv; |
| struct flow_offload_tuple tuple = {}; |
| enum flow_offload_tuple_dir dir; |
| struct flow_offload *flow; |
| struct net_device *outdev; |
| const struct rtable *rt; |
| struct iphdr *iph; |
| __be32 nexthop; |
| |
| if (skb->protocol != htons(ETH_P_IP)) |
| return NF_ACCEPT; |
| |
| if (nf_flow_tuple_ip(skb, state->in, &tuple) < 0) |
| return NF_ACCEPT; |
| |
| tuplehash = flow_offload_lookup(flow_table, &tuple); |
| if (tuplehash == NULL) |
| return NF_ACCEPT; |
| |
| outdev = dev_get_by_index_rcu(state->net, tuplehash->tuple.oifidx); |
| if (!outdev) |
| return NF_ACCEPT; |
| |
| dir = tuplehash->tuple.dir; |
| flow = container_of(tuplehash, struct flow_offload, tuplehash[dir]); |
| |
| rt = (const struct rtable *)flow->tuplehash[dir].tuple.dst_cache; |
| if (unlikely(nf_flow_exceeds_mtu(skb, rt))) |
| return NF_ACCEPT; |
| |
| if (skb_try_make_writable(skb, sizeof(*iph))) |
| return NF_DROP; |
| |
| if (flow->flags & (FLOW_OFFLOAD_SNAT | FLOW_OFFLOAD_DNAT) && |
| nf_flow_nat_ip(flow, skb, dir) < 0) |
| return NF_DROP; |
| |
| flow->timeout = (u32)jiffies + NF_FLOW_TIMEOUT; |
| iph = ip_hdr(skb); |
| ip_decrease_ttl(iph); |
| |
| skb->dev = outdev; |
| nexthop = rt_nexthop(rt, flow->tuplehash[!dir].tuple.src_v4.s_addr); |
| neigh_xmit(NEIGH_ARP_TABLE, outdev, &nexthop, skb); |
| |
| return NF_STOLEN; |
| } |
| EXPORT_SYMBOL_GPL(nf_flow_offload_ip_hook); |
| |
| static struct nf_flowtable_type flowtable_ipv4 = { |
| .family = NFPROTO_IPV4, |
| .params = &nf_flow_offload_rhash_params, |
| .gc = nf_flow_offload_work_gc, |
| .free = nf_flow_table_free, |
| .hook = nf_flow_offload_ip_hook, |
| .owner = THIS_MODULE, |
| }; |
| |
| static int __init nf_flow_ipv4_module_init(void) |
| { |
| nft_register_flowtable_type(&flowtable_ipv4); |
| |
| return 0; |
| } |
| |
| static void __exit nf_flow_ipv4_module_exit(void) |
| { |
| nft_unregister_flowtable_type(&flowtable_ipv4); |
| } |
| |
| module_init(nf_flow_ipv4_module_init); |
| module_exit(nf_flow_ipv4_module_exit); |
| |
| MODULE_LICENSE("GPL"); |
| MODULE_AUTHOR("Pablo Neira Ayuso <pablo@netfilter.org>"); |
| MODULE_ALIAS_NF_FLOWTABLE(AF_INET); |