This patch adds the generic software flow offload infrastructure. This
allows users to configure fast path for established flows that will not
follow the classic forwarding path.
This adds a new hook at netfilter ingress for each existing interface.
For each packet that hits the hook, we look up for an existing flow in
the table, if there is a hit, the packet is forwarded by using the
gateway and interfaces that are cached in the flow table entry.
This comes with a kernel thread to release flow table entries if no
packets are seen after a little while, so the flow table entry is
released.
Signed-off-by: Pablo Neira Ayuso <pablo@xxxxxxxxxxxxx>
---
include/net/flow_offload.h | 67 +++++++
net/netfilter/Kconfig | 7 +
net/netfilter/Makefile | 3 +
net/netfilter/nf_flow_offload.c | 386 ++++++++++++++++++++++++++++++++++++++++
4 files changed, 463 insertions(+)
create mode 100644 include/net/flow_offload.h
create mode 100644 net/netfilter/nf_flow_offload.c
diff --git a/include/net/flow_offload.h b/include/net/flow_offload.h
new file mode 100644
index 000000000000..30bfca7ed3f1
--- /dev/null
+++ b/include/net/flow_offload.h
@@ -0,0 +1,67 @@
+#ifndef _FLOW_OFFLOAD_H
+#define _FLOW_OFFLOAD_H
+
+#include <linux/in.h>
+#include <linux/in6.h>
+#include <linux/netdevice.h>
+#include <linux/rhashtable.h>
+#include <linux/rcupdate.h>
+
+enum flow_offload_tuple_dir {
+ FLOW_OFFLOAD_DIR_ORIGINAL,
+ FLOW_OFFLOAD_DIR_REPLY,
+ __FLOW_OFFLOAD_DIR_MAX = FLOW_OFFLOAD_DIR_REPLY,
+};
+#define FLOW_OFFLOAD_DIR_MAX (__FLOW_OFFLOAD_DIR_MAX + 1)
+
+struct flow_offload_tuple {
+ union {
+ struct in_addr src_v4;
+ struct in6_addr src_v6;
+ };
+ union {
+ struct in_addr dst_v4;
+ struct in6_addr dst_v6;
+ };
+ struct {
+ __be16 src_port;
+ __be16 dst_port;
+ };
+
+ u8 l3proto;
+ u8 l4proto;
+ u8 dir;
+
+ int iifidx;
+ int oifidx;
+
+ union {
+ __be32 gateway;
+ struct in6_addr gateway6;
+ };
+};
+
+struct flow_offload_tuple_rhash {
+ struct rhash_head node;
+ struct flow_offload_tuple tuple;
+};
+
+#define FLOW_OFFLOAD_SNAT 0x1
+#define FLOW_OFFLOAD_DNAT 0x2
+#define FLOW_OFFLOAD_HW 0x4
+
+struct flow_offload {
+ struct flow_offload_tuple_rhash tuplehash[FLOW_OFFLOAD_DIR_MAX];
+ u32 flags;
+ union {
+ /* Your private driver data here. */
+ u32 timeout;
+ };
+ struct rcu_head rcu_head;
+};
+
+int flow_offload_add(struct flow_offload *flow);
+void flow_offload_del(struct flow_offload *flow);
+struct flow_offload_tuple_rhash *flow_offload_lookup(struct flow_offload_tuple *tuple);
+
+#endif /* _FLOW_OFFLOAD_H */
diff --git a/net/netfilter/Kconfig b/net/netfilter/Kconfig
index e4a13cc8a2e7..f022ca91f49d 100644
--- a/net/netfilter/Kconfig
+++ b/net/netfilter/Kconfig
@@ -436,6 +436,13 @@ config NETFILTER_SYNPROXY
endif # NF_CONNTRACK
+config NF_FLOW_OFFLOAD
+ tristate "Netfilter Generic Flow Offload (GFO) module"
+ help
+ This option adds the flow table core infrastructure.
+
+ To compile it as a module, choose M here.
+
config NF_TABLES
select NETFILTER_NETLINK
tristate "Netfilter nf_tables support"
diff --git a/net/netfilter/Makefile b/net/netfilter/Makefile
index d3891c93edd6..518f54113e06 100644
--- a/net/netfilter/Makefile
+++ b/net/netfilter/Makefile
@@ -69,6 +69,9 @@ obj-$(CONFIG_NETFILTER_SYNPROXY) += nf_synproxy_core.o
# generic packet duplication from netdev family
obj-$(CONFIG_NF_DUP_NETDEV) += nf_dup_netdev.o
+# generic flow table
+obj-$(CONFIG_NF_FLOW_OFFLOAD)+= nf_flow_offload.o
+
# nf_tables
nf_tables-objs := nf_tables_core.o nf_tables_api.o nf_tables_trace.o \
nft_immediate.o nft_cmp.o nft_range.o nft_bitwise.o \
diff --git a/net/netfilter/nf_flow_offload.c b/net/netfilter/nf_flow_offload.c
new file mode 100644
index 000000000000..c967b29d11a6
--- /dev/null
+++ b/net/netfilter/nf_flow_offload.c
@@ -0,0 +1,386 @@
+#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/flow_offload.h>
+/* For layer 4 checksum field offset. */
+#include <linux/tcp.h>
+#include <linux/udp.h>
+#include <linux/icmpv6.h>
+
+static struct rhashtable flow_table;
+
+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_rhash *x = ptr;
+ const struct flow_offload_tuple *tuple = arg->key;
+
+ 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,
+};
+
+#define NF_FLOW_LIFETIME 15
+
+int flow_offload_add(struct flow_offload *flow)
+{
+ flow->timeout = (u32)jiffies;
+
+ rhashtable_insert_fast(&flow_table, &flow->tuplehash[0].node,
+ flow_offload_rhash_params);
+ rhashtable_insert_fast(&flow_table, &flow->tuplehash[1].node,
+ flow_offload_rhash_params);
+ return 0;
+}
+EXPORT_SYMBOL_GPL(flow_offload_add);
+
+void flow_offload_del(struct flow_offload *flow)
+{
+ rhashtable_remove_fast(&flow_table, &flow->tuplehash[0].node,
+ flow_offload_rhash_params);
+ rhashtable_remove_fast(&flow_table, &flow->tuplehash[1].node,
+ flow_offload_rhash_params);
+ kfree_rcu(flow, rcu_head);
+}
+EXPORT_SYMBOL_GPL(flow_offload_del);
+
+struct flow_offload_tuple_rhash *
+flow_offload_lookup(struct flow_offload_tuple *tuple)
+{
+ return rhashtable_lookup_fast(&flow_table, tuple,
+ flow_offload_rhash_params);
+}
+EXPORT_SYMBOL_GPL(flow_offload_lookup);
+
+static void nf_flow_offload_work_gc(struct work_struct *work);
+
+static DECLARE_DEFERRABLE_WORK(nf_flow_offload_gc,
+ nf_flow_offload_work_gc);
+
+static inline bool nf_flow_has_expired(const struct flow_offload *flow)
+{
+ return (__s32)(flow->timeout - (u32)jiffies) <= 0;
+}
+
+static void nf_flow_offload_work_gc(struct work_struct *work)
+{
+ struct flow_offload_tuple_rhash *tuplehash;
+ struct rhashtable_iter hti;
+ struct flow_offload *flow;
+ int err, counter = 0;
+
+ rhashtable_walk_init(&flow_table, &hti, GFP_KERNEL);
+ err = rhashtable_walk_start(&hti);
+ if (err && err != -EAGAIN)
+ goto out;
+
+ while ((tuplehash = rhashtable_walk_next(&hti))) {
+ if (IS_ERR(tuplehash)) {
+ err = PTR_ERR(tuplehash);
+ if (err != -EAGAIN)
+ goto out;
+
+ continue;
+ }
+ if (tuplehash->tuple.dir)
+ continue;
+
+ flow = container_of(tuplehash, struct flow_offload, tuplehash[0]);
+
+ if (nf_flow_has_expired(flow))
+ flow_offload_del(flow);
+
+ counter++;
+ }
+
+ rhashtable_walk_stop(&hti);
+ rhashtable_walk_exit(&hti);
+
+out:
+ queue_delayed_work(system_power_efficient_wq, &nf_flow_offload_gc,
+ msecs_to_jiffies(1000));
+}
+
+static int nf_flow_snat_tcp(struct iphdr *iph,
+ const struct flow_offload *flow,
+ 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_snat_udp(struct iphdr *iph,
+ const struct flow_offload *flow,
+ 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_snat(struct iphdr *iph,
+ const struct flow_offload *flow,
+ enum flow_offload_tuple_dir dir, struct sk_buff *skb)
+{
+ __be32 new_addr, addr;
+ unsigned int thoff;
+
+ if (skb_try_make_writable(skb, sizeof(*iph)))
+ return NF_DROP;
+
+ 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);
+
+ ip_decrease_ttl(iph);
+
+ thoff = iph->ihl * 4;
+
+ switch (iph->protocol) {
+ case IPPROTO_TCP:
+ if (nf_flow_snat_tcp(iph, flow, skb, thoff, addr, new_addr) < 0)
+ return NF_DROP;
+ break;
+ case IPPROTO_UDP:
+ if (nf_flow_snat_udp(iph, flow, skb, thoff, addr, new_addr) < 0)
+ return NF_DROP;
+ break;
+ }
+
+ return 0;
+}
+
+/* Similar to rt_nexthop(). */
+static inline __be32 nf_flow_nexthop(__be32 nexthop, __be32 daddr)
+{
+ if (nexthop)
+ return nexthop;
+
+ return daddr;
+}
+
+struct flow_ports {
+ __be16 src, dst;
+};
+
+static int nf_flow_tuple_ip(struct iphdr *iph, struct sk_buff *skb,
+ struct flow_offload_tuple *tuple)
+{
+ struct flow_ports *ports;
+ unsigned int thoff;
+
+ 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 flow_offload_tuple tuple = {};
+ struct flow_offload *flow;
+ struct net_device *outdev;
+ struct iphdr *iph;
+ __be32 nexthop;
+ int err;
+
+ switch (skb->protocol) {
+ case cpu_to_be16(ETH_P_IP):
+ if (!pskb_may_pull(skb, sizeof(*iph)))
+ return NF_ACCEPT;
+
+ iph = ip_hdr(skb);
+ if (ip_is_fragment(iph))
+ return NF_ACCEPT;
+
+ err = nf_flow_tuple_ip(iph, skb, &tuple);
+ if (err < 0)
+ return NF_ACCEPT;
+ break;
+ default:
+ return NF_ACCEPT;
+ }
+
+ tuplehash = flow_offload_lookup(&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 &&
+ nf_flow_snat(iph, flow, tuplehash->tuple.dir, skb) < 0)
+ return NF_DROP;
+
+ skb->dev = outdev;
+ nexthop = nf_flow_nexthop(tuplehash->tuple.gateway, iph->daddr);
+
+ neigh_xmit(NEIGH_ARP_TABLE, outdev, &nexthop, skb);
+
+ return NF_STOLEN;
+}
+
+static LIST_HEAD(nf_flow_hook_list);
+
+struct nf_flow_hook_entry {
+ struct list_head head;
+ struct nf_hook_ops ops;
+};
+
+static int __init nf_flow_offload_module_init(void)
+{
+ struct rhashtable_params params = flow_offload_rhash_params;
+ struct nf_hook_ops flow_offload_hook = {
+ .hook = nf_flow_offload_hook,
+ .pf = NFPROTO_NETDEV,
+ .hooknum = NF_NETDEV_INGRESS,
+ .priority = -100,
+ };
+ struct nf_flow_hook_entry *entry;
+ struct net_device *dev;
+ int err;
+
+ params.key_len = offsetof(struct flow_offload_tuple, dir);
+ err = rhashtable_init(&flow_table, ¶ms);
+ if (err < 0)
+ return err;
+
+ rtnl_lock();
+ for_each_netdev(&init_net, dev) {
+ entry = kmalloc(sizeof(*entry), GFP_KERNEL);
+ if (!entry) {
+ rtnl_unlock();
+ return -ENOMEM;
+ }
+ entry->ops = flow_offload_hook;
+ entry->ops.dev = dev;
+ list_add_tail(&entry->head, &nf_flow_hook_list);
+
+ err = nf_register_net_hook(&init_net, &entry->ops);
+ if (err < 0)
+ return err;
+
+ pr_info("register flow table for device %s\n", dev->name);
+ }
+ rtnl_unlock();
+
+ queue_delayed_work(system_power_efficient_wq, &nf_flow_offload_gc,
+ msecs_to_jiffies(1000));
+ return err;
+}
+
+static void flow_offload_destroy(void *ptr, void *arg)
+{
+ kfree(ptr);
+}
+
+static void __exit nf_flow_offload_module_exit(void)
+{
+ struct nf_flow_hook_entry *entry, *next;
+
+ cancel_delayed_work_sync(&nf_flow_offload_gc);
+ list_for_each_entry_safe(entry, next, &nf_flow_hook_list, head) {
+ pr_info("unregister flow table for device %s\n",
+ entry->ops.dev->name);
+ nf_unregister_net_hook(&init_net, &entry->ops);
+ list_del(&entry->head);
+ kfree(entry);
+ }
+ rhashtable_free_and_destroy(&flow_table, flow_offload_destroy, NULL);
+}
+
+module_init(nf_flow_offload_module_init);
+module_exit(nf_flow_offload_module_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Pablo Neira Ayuso <pablo@xxxxxxxxxxxxx>");
--
2.11.0
--
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