This patch adds the IPv4 flow table type, that implements the datapath
flow table to forward IPv4 traffic. Rationale is:
1) Look up for the packet in the flow table, from the ingress hook.
2) If there's a hit, decrement ttl and pass it on to the neighbour layer
for transmission.
3) If there's a miss, packet is passed up to the classic forwarding
path.
This patch also supports layer 3 source and destination NAT.
Signed-off-by: Pablo Neira Ayuso <pablo@xxxxxxxxxxxxx>
---
net/ipv4/netfilter/Kconfig | 8 +
net/ipv4/netfilter/Makefile | 3 +
net/ipv4/netfilter/nf_flow_table_ipv4.c | 316 ++++++++++++++++++++++++++++++++
3 files changed, 327 insertions(+)
create mode 100644 net/ipv4/netfilter/nf_flow_table_ipv4.c
diff --git a/net/ipv4/netfilter/Kconfig b/net/ipv4/netfilter/Kconfig
index c11eb1744ab1..8b430c1744c4 100644
--- a/net/ipv4/netfilter/Kconfig
+++ b/net/ipv4/netfilter/Kconfig
@@ -177,6 +177,14 @@ config NF_NAT_H323
endif # NF_NAT_IPV4
+config NF_FLOW_TABLE_IPV4
+ select NF_FLOW_TABLE
+ tristate "Netfilter flow table IPv4 module"
+ help
+ This option adds the flow table IPv4 support.
+
+ To compile it as a module, choose M here.
+
config IP_NF_IPTABLES
tristate "IP tables support (required for filtering/masq/NAT)"
default m if NETFILTER_ADVANCED=n
diff --git a/net/ipv4/netfilter/Makefile b/net/ipv4/netfilter/Makefile
index f462fee66ac8..ae39e1c569a8 100644
--- a/net/ipv4/netfilter/Makefile
+++ b/net/ipv4/netfilter/Makefile
@@ -52,6 +52,9 @@ obj-$(CONFIG_IP_NF_NAT) += iptable_nat.o
obj-$(CONFIG_IP_NF_RAW) += iptable_raw.o
obj-$(CONFIG_IP_NF_SECURITY) += iptable_security.o
+# flow table support
+obj-$(CONFIG_NF_FLOW_TABLE_IPV4) += nf_flow_table_ipv4.o
+
# matches
obj-$(CONFIG_IP_NF_MATCH_AH) += ipt_ah.o
obj-$(CONFIG_IP_NF_MATCH_RPFILTER) += ipt_rpfilter.o
diff --git a/net/ipv4/netfilter/nf_flow_table_ipv4.c b/net/ipv4/netfilter/nf_flow_table_ipv4.c
new file mode 100644
index 000000000000..090a3fbcf211
--- /dev/null
+++ b/net/ipv4/netfilter/nf_flow_table_ipv4.c
@@ -0,0 +1,316 @@
+#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_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_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_l4proto(struct sk_buff *skb, struct iphdr *iph,
+ unsigned int thoff, __be32 addr, __be32 new_addr)
+{
+ csum_replace4(&iph->check, addr, new_addr);
+
+ switch (iph->protocol) {
+ case IPPROTO_TCP:
+ if (nf_flow_nat_tcp(skb, thoff, addr, new_addr) < 0)
+ return NF_DROP;
+ break;
+ case IPPROTO_UDP:
+ if (nf_flow_nat_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;
+ }
+
+ return nf_flow_nat_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_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)
+{
+ unsigned int thoff;
+ struct iphdr *iph;
+
+ if (skb_try_make_writable(skb, sizeof(*iph)))
+ return -1;
+
+ iph = ip_hdr(skb);
+ thoff = iph->ihl * 4;
+
+ if (flow->flags & FLOW_OFFLOAD_SNAT &&
+ nf_flow_snat_ip(flow, skb, iph, thoff, dir) < 0)
+ return -1;
+ if (flow->flags & FLOW_OFFLOAD_DNAT &&
+ nf_flow_dnat_ip(flow, skb, iph, thoff, dir) < 0)
+ return -1;
+
+ return 0;
+}
+
+/* Similar to rt_nexthop(). */
+static inline void
+nf_flow_nexthop(const struct flow_offload *flow,
+ union nf_inet_addr *nexthop, enum flow_offload_tuple_dir dir)
+{
+ if (flow->tuplehash[dir].tuple.gateway) {
+ nexthop->ip = flow->tuplehash[dir].tuple.gateway;
+ return;
+ }
+
+ nexthop->ip = flow->tuplehash[!dir].tuple.src_v4.s_addr;
+}
+
+struct flow_ports {
+ __be16 src, dst;
+};
+
+static bool ip_has_options(unsigned int thoff)
+{
+ return thoff > sizeof(struct iphdr);
+}
+
+static int nf_flow_tuple_ip(struct sk_buff *skb,
+ 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->src;
+ tuple->dst_port = ports->dst;
+ tuple->l3proto = AF_INET;
+ tuple->l4proto = iph->protocol;
+
+ return 0;
+}
+
+#define NF_FLOW_TIMEOUT (30 * HZ)
+
+static unsigned int
+nf_flow_offload_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 = {};
+ union nf_inet_addr nexthop;
+ struct flow_offload *flow;
+ struct net_device *outdev;
+ struct iphdr *iph;
+
+ if (nf_flow_tuple_ip(skb, &tuple) < 0)
+ return NF_ACCEPT;
+
+ tuplehash = flow_offload_lookup(flow_table, &tuple);
+ if (tuplehash == NULL)
+ return NF_ACCEPT;
+
+ outdev = dev_get_by_index_rcu(&init_net, tuplehash->tuple.oifidx);
+ if (!outdev)
+ return NF_ACCEPT;
+
+ flow = container_of(tuplehash, struct flow_offload,
+ tuplehash[tuplehash->tuple.dir]);
+
+ flow->timeout = (u32)jiffies + NF_FLOW_TIMEOUT;
+
+ if (flow->flags & (FLOW_OFFLOAD_SNAT | FLOW_OFFLOAD_DNAT) &&
+ nf_flow_nat_ip(flow, skb, tuplehash->tuple.dir) < 0)
+ return NF_DROP;
+
+ iph = ip_hdr(skb);
+ ip_decrease_ttl(iph);
+
+ skb->dev = outdev;
+ nf_flow_nexthop(flow, &nexthop, tuplehash->tuple.dir);
+
+ neigh_xmit(NEIGH_ARP_TABLE, outdev, &nexthop, skb);
+
+ return NF_STOLEN;
+}
+
+static u32 flow_offload_hash(const void *data, u32 len, u32 seed)
+{
+ const struct flow_offload_tuple *tuple = data;
+
+ return jhash(tuple, offsetof(struct flow_offload_tuple, l4proto), seed);
+}
+
+static u32 flow_offload_hash_obj(const void *data, u32 len, u32 seed)
+{
+ const struct flow_offload_tuple_rhash *tuplehash = data;
+
+ return jhash(&tuplehash->tuple, offsetof(struct flow_offload_tuple, l4proto), seed);
+}
+
+static int flow_offload_hash_cmp(struct rhashtable_compare_arg *arg,
+ const void *ptr)
+{
+ const struct flow_offload_tuple *tuple = arg->key;
+ const struct flow_offload_tuple_rhash *x = ptr;
+
+ if (memcmp(&x->tuple, tuple, offsetof(struct flow_offload_tuple, l4proto)))
+ return 1;
+
+ return 0;
+}
+
+static const struct rhashtable_params flow_offload_rhash_params = {
+ .head_offset = offsetof(struct flow_offload_tuple_rhash, node),
+ .hashfn = flow_offload_hash,
+ .obj_hashfn = flow_offload_hash_obj,
+ .obj_cmpfn = flow_offload_hash_cmp,
+ .automatic_shrinking = true,
+};
+
+static int nf_flow_table_ipv4_init(struct nf_flowtable *flow_table)
+{
+ INIT_DEFERRABLE_WORK(&flow_table->gc_work, nf_flow_offload_work_gc);
+ queue_delayed_work(system_power_efficient_wq, &flow_table->gc_work, HZ);
+ return 0;
+}
+
+static void nf_flow_table_ipv4_destroy(struct nf_flowtable *flow_table)
+{
+ cancel_delayed_work_sync(&flow_table->gc_work);
+}
+
+static struct nf_flowtable_type flowtable_ipv4 = {
+ .family = NFPROTO_IPV4,
+ .init = nf_flow_table_ipv4_init,
+ .destroy = nf_flow_table_ipv4_destroy,
+ .params = &flow_offload_rhash_params,
+ .hook = nf_flow_offload_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@xxxxxxxxxxxxx>");
+MODULE_ALIAS_NFT_FLOWTABLE(AF_INET);
--
2.11.0
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