kernel: add minimal TCP state tracking to flow offload support

Fixes issues with connections hanging after >30 seconds idle time

Signed-off-by: Felix Fietkau <nbd@nbd.name>

5 files changed, 293 insertions, 0 deletions

diff --git a/target/linux/generic/backport-4.14/360-netfilter-nf_flow_table-make-flow_offload_dead-inlin.patch b/target/linux/generic/backport-4.14/360-netfilter-nf_flow_table-make-flow_offload_dead-inlin.patch
new file mode 100644
index 0000000000..d33400c729
--- /dev/null
+++ b/target/linux/generic/backport-4.14/360-netfilter-nf_flow_table-make-flow_offload_dead-inlin.patch
@@ -0,0 +1,38 @@
+From: Felix Fietkau <nbd@nbd.name>
+Date: Sun, 25 Feb 2018 15:37:27 +0100
+Subject: [PATCH] netfilter: nf_flow_table: make flow_offload_dead inline
+
+It is too trivial to keep as a separate exported function
+
+Signed-off-by: Felix Fietkau <nbd@nbd.name>
+---
+
+--- a/include/net/netfilter/nf_flow_table.h
++++ b/include/net/netfilter/nf_flow_table.h
+@@ -103,7 +103,10 @@ void nf_flow_table_cleanup(struct net *n
+ int nf_flow_table_init(struct nf_flowtable *flow_table);
+ void nf_flow_table_free(struct nf_flowtable *flow_table);
+ 
+-void flow_offload_dead(struct flow_offload *flow);
++static inline void flow_offload_dead(struct flow_offload *flow)
++{
++	flow->flags |= FLOW_OFFLOAD_DYING;
++}
+ 
+ int nf_flow_snat_port(const struct flow_offload *flow,
+ 		      struct sk_buff *skb, unsigned int thoff,
+--- a/net/netfilter/nf_flow_table_core.c
++++ b/net/netfilter/nf_flow_table_core.c
+@@ -113,12 +113,6 @@ void flow_offload_free(struct flow_offlo
+ }
+ EXPORT_SYMBOL_GPL(flow_offload_free);
+ 
+-void flow_offload_dead(struct flow_offload *flow)
+-{
+-	flow->flags |= FLOW_OFFLOAD_DYING;
+-}
+-EXPORT_SYMBOL_GPL(flow_offload_dead);
+-
+ static u32 flow_offload_hash(const void *data, u32 len, u32 seed)
+ {
+ 	const struct flow_offload_tuple *tuple = data;
diff --git a/target/linux/generic/backport-4.14/361-netfilter-nf_flow_table-add-a-new-flow-state-for-tea.patch b/target/linux/generic/backport-4.14/361-netfilter-nf_flow_table-add-a-new-flow-state-for-tea.patch
new file mode 100644
index 0000000000..83751d8cb1
--- /dev/null
+++ b/target/linux/generic/backport-4.14/361-netfilter-nf_flow_table-add-a-new-flow-state-for-tea.patch
@@ -0,0 +1,74 @@
+From: Felix Fietkau <nbd@nbd.name>
+Date: Sun, 25 Feb 2018 15:38:31 +0100
+Subject: [PATCH] netfilter: nf_flow_table: add a new flow state for
+ tearing down offloading
+
+Will be used to tear down the offload entry while keeping the conntrack
+entry alive.
+
+Signed-off-by: Felix Fietkau <nbd@nbd.name>
+---
+
+--- a/include/net/netfilter/nf_flow_table.h
++++ b/include/net/netfilter/nf_flow_table.h
+@@ -68,6 +68,7 @@ struct flow_offload_tuple_rhash {
+ #define FLOW_OFFLOAD_SNAT	0x1
+ #define FLOW_OFFLOAD_DNAT	0x2
+ #define FLOW_OFFLOAD_DYING	0x4
++#define FLOW_OFFLOAD_TEARDOWN	0x8
+ 
+ struct flow_offload {
+ 	struct flow_offload_tuple_rhash		tuplehash[FLOW_OFFLOAD_DIR_MAX];
+@@ -108,6 +109,11 @@ static inline void flow_offload_dead(str
+ 	flow->flags |= FLOW_OFFLOAD_DYING;
+ }
+ 
++static inline void flow_offload_teardown(struct flow_offload *flow)
++{
++	flow->flags |= FLOW_OFFLOAD_TEARDOWN;
++}
++
+ int nf_flow_snat_port(const struct flow_offload *flow,
+ 		      struct sk_buff *skb, unsigned int thoff,
+ 		      u8 protocol, enum flow_offload_tuple_dir dir);
+--- a/net/netfilter/nf_flow_table_core.c
++++ b/net/netfilter/nf_flow_table_core.c
+@@ -226,11 +226,6 @@ static inline bool nf_flow_has_expired(c
+ 	return (__s32)(flow->timeout - (u32)jiffies) <= 0;
+ }
+ 
+-static inline bool nf_flow_is_dying(const struct flow_offload *flow)
+-{
+-	return flow->flags & FLOW_OFFLOAD_DYING;
+-}
+-
+ static int nf_flow_offload_gc_step(struct nf_flowtable *flow_table)
+ {
+ 	struct flow_offload_tuple_rhash *tuplehash;
+@@ -258,7 +253,8 @@ static int nf_flow_offload_gc_step(struc
+ 		flow = container_of(tuplehash, struct flow_offload, tuplehash[0]);
+ 
+ 		if (nf_flow_has_expired(flow) ||
+-		    nf_flow_is_dying(flow))
++		    (flow->flags & (FLOW_OFFLOAD_DYING |
++				    FLOW_OFFLOAD_TEARDOWN)))
+ 			flow_offload_del(flow_table, flow);
+ 	}
+ out:
+@@ -419,10 +415,14 @@ static void nf_flow_table_do_cleanup(str
+ {
+ 	struct net_device *dev = data;
+ 
+-	if (dev && flow->tuplehash[0].tuple.iifidx != dev->ifindex)
++	if (!dev) {
++		flow_offload_teardown(flow);
+ 		return;
++	}
+ 
+-	flow_offload_dead(flow);
++	if (flow->tuplehash[0].tuple.iifidx == dev->ifindex ||
++	    flow->tuplehash[1].tuple.iifidx == dev->ifindex)
++		flow_offload_dead(flow);
+ }
+ 
+ static void nf_flow_table_iterate_cleanup(struct nf_flowtable *flowtable,
diff --git a/target/linux/generic/backport-4.14/362-netfilter-nf_flow_table-in-flow_offload_lookup-skip-.patch b/target/linux/generic/backport-4.14/362-netfilter-nf_flow_table-in-flow_offload_lookup-skip-.patch
new file mode 100644
index 0000000000..e6d7dd8fc8
--- /dev/null
+++ b/target/linux/generic/backport-4.14/362-netfilter-nf_flow_table-in-flow_offload_lookup-skip-.patch
@@ -0,0 +1,36 @@
+From: Felix Fietkau <nbd@nbd.name>
+Date: Sun, 25 Feb 2018 15:39:56 +0100
+Subject: [PATCH] netfilter: nf_flow_table: in flow_offload_lookup, skip
+ entries being deleted
+
+Preparation for sending flows back to the slow path
+
+Signed-off-by: Felix Fietkau <nbd@nbd.name>
+---
+
+--- a/net/netfilter/nf_flow_table_core.c
++++ b/net/netfilter/nf_flow_table_core.c
+@@ -178,8 +178,21 @@ struct flow_offload_tuple_rhash *
+ flow_offload_lookup(struct nf_flowtable *flow_table,
+ 		    struct flow_offload_tuple *tuple)
+ {
+-	return rhashtable_lookup_fast(&flow_table->rhashtable, tuple,
+-				      nf_flow_offload_rhash_params);
++	struct flow_offload_tuple_rhash *tuplehash;
++	struct flow_offload *flow;
++	int dir;
++
++	tuplehash = rhashtable_lookup_fast(&flow_table->rhashtable, tuple,
++					   nf_flow_offload_rhash_params);
++	if (!tuplehash)
++		return NULL;
++
++	dir = tuplehash->tuple.dir;
++	flow = container_of(tuplehash, struct flow_offload, tuplehash[dir]);
++	if (flow->flags & (FLOW_OFFLOAD_DYING | FLOW_OFFLOAD_TEARDOWN))
++		return NULL;
++
++	return tuplehash;
+ }
+ EXPORT_SYMBOL_GPL(flow_offload_lookup);
+ 
diff --git a/target/linux/generic/backport-4.14/363-netfilter-nf_flow_table-add-support-for-sending-flow.patch b/target/linux/generic/backport-4.14/363-netfilter-nf_flow_table-add-support-for-sending-flow.patch
new file mode 100644
index 0000000000..b4d80a911b
--- /dev/null
+++ b/target/linux/generic/backport-4.14/363-netfilter-nf_flow_table-add-support-for-sending-flow.patch
@@ -0,0 +1,64 @@
+From: Felix Fietkau <nbd@nbd.name>
+Date: Sun, 25 Feb 2018 15:41:11 +0100
+Subject: [PATCH] netfilter: nf_flow_table: add support for sending flows
+ back to the slow path
+
+Reset the timeout. For TCP, also set the state to indicate to use the
+next incoming packets to reset window tracking.
+This allows the slow path to take over again once the offload state has
+been torn down
+
+Signed-off-by: Felix Fietkau <nbd@nbd.name>
+---
+
+--- a/net/netfilter/nf_flow_table_core.c
++++ b/net/netfilter/nf_flow_table_core.c
+@@ -100,6 +100,36 @@ err_ct_refcnt:
+ }
+ EXPORT_SYMBOL_GPL(flow_offload_alloc);
+ 
++static void flow_offload_fixup_ct_state(struct nf_conn *ct)
++{
++	const struct nf_conntrack_l4proto *l4proto;
++	struct net *net = nf_ct_net(ct);
++	unsigned int *timeouts;
++	unsigned int timeout;
++	int l4num;
++
++	l4num = nf_ct_protonum(ct);
++	l4proto = __nf_ct_l4proto_find(nf_ct_l3num(ct), l4num);
++	if (!l4proto)
++		return;
++
++	timeouts = l4proto->get_timeouts(net);
++	if (!timeouts)
++		return;
++
++	if (l4num == IPPROTO_TCP) {
++		timeout = timeouts[TCP_CONNTRACK_ESTABLISHED];
++		ct->proto.tcp.state = TCP_CONNTRACK_IGNORE;
++	} else if (l4num == IPPROTO_UDP) {
++		timeout = timeouts[UDP_CT_REPLIED];
++	} else {
++		return;
++	}
++
++	ct->timeout = nfct_time_stamp + timeout;
++	clear_bit(IPS_OFFLOAD_BIT, &ct->status);
++}
++
+ void flow_offload_free(struct flow_offload *flow)
+ {
+ 	struct flow_offload_entry *e;
+@@ -107,7 +137,10 @@ void flow_offload_free(struct flow_offlo
+ 	dst_release(flow->tuplehash[FLOW_OFFLOAD_DIR_ORIGINAL].tuple.dst_cache);
+ 	dst_release(flow->tuplehash[FLOW_OFFLOAD_DIR_REPLY].tuple.dst_cache);
+ 	e = container_of(flow, struct flow_offload_entry, flow);
+-	nf_ct_delete(e->ct, 0, 0);
++	if (flow->flags & FLOW_OFFLOAD_DYING)
++		nf_ct_delete(e->ct, 0, 0);
++	else
++		flow_offload_fixup_ct_state(e->ct);
+ 	nf_ct_put(e->ct);
+ 	kfree_rcu(e, rcu_head);
+ }
diff --git a/target/linux/generic/backport-4.14/364-netfilter-nf_flow_table-tear-down-TCP-flows-if-RST-o.patch b/target/linux/generic/backport-4.14/364-netfilter-nf_flow_table-tear-down-TCP-flows-if-RST-o.patch
new file mode 100644
index 0000000000..8b0024cd8d
--- /dev/null
+++ b/target/linux/generic/backport-4.14/364-netfilter-nf_flow_table-tear-down-TCP-flows-if-RST-o.patch
@@ -0,0 +1,81 @@
+From: Felix Fietkau <nbd@nbd.name>
+Date: Sun, 25 Feb 2018 15:42:58 +0100
+Subject: [PATCH] netfilter: nf_flow_table: tear down TCP flows if RST or
+ FIN was seen
+
+Allow the slow path to handle the shutdown of the connection with proper
+timeouts
+
+Signed-off-by: Felix Fietkau <nbd@nbd.name>
+---
+
+--- a/net/netfilter/nf_flow_table_ip.c
++++ b/net/netfilter/nf_flow_table_ip.c
+@@ -15,6 +15,23 @@
+ #include <linux/tcp.h>
+ #include <linux/udp.h>
+ 
++static int nf_flow_tcp_state_check(struct flow_offload *flow,
++				   struct sk_buff *skb, unsigned int thoff)
++{
++	struct tcphdr *tcph;
++
++	if (!pskb_may_pull(skb, thoff + sizeof(*tcph)))
++		return -1;
++
++	tcph = (void *)(skb_network_header(skb) + thoff);
++	if (unlikely(tcph->fin || tcph->rst)) {
++		flow_offload_teardown(flow);
++		return -1;
++	}
++
++	return 0;
++}
++
+ static int nf_flow_nat_ip_tcp(struct sk_buff *skb, unsigned int thoff,
+ 			      __be32 addr, __be32 new_addr)
+ {
+@@ -118,10 +135,9 @@ static int nf_flow_dnat_ip(const struct
+ }
+ 
+ static int nf_flow_nat_ip(const struct flow_offload *flow, struct sk_buff *skb,
+-			  enum flow_offload_tuple_dir dir)
++			  unsigned int thoff, 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 ||
+@@ -201,6 +217,7 @@ nf_flow_offload_ip_hook(void *priv, stru
+ 	struct flow_offload *flow;
+ 	struct net_device *outdev;
+ 	const struct rtable *rt;
++	unsigned int thoff;
+ 	struct iphdr *iph;
+ 	__be32 nexthop;
+ 
+@@ -229,8 +246,12 @@ nf_flow_offload_ip_hook(void *priv, stru
+ 	if (skb_try_make_writable(skb, sizeof(*iph)))
+ 		return NF_DROP;
+ 
++	thoff = ip_hdr(skb)->ihl * 4;
++	if (nf_flow_tcp_state_check(flow, skb, thoff))
++		return NF_ACCEPT;
++
+ 	if (flow->flags & (FLOW_OFFLOAD_SNAT | FLOW_OFFLOAD_DNAT) &&
+-	    nf_flow_nat_ip(flow, skb, dir) < 0)
++	    nf_flow_nat_ip(flow, skb, thoff, dir) < 0)
+ 		return NF_DROP;
+ 
+ 	flow->timeout = (u32)jiffies + NF_FLOW_TIMEOUT;
+@@ -438,6 +459,9 @@ nf_flow_offload_ipv6_hook(void *priv, st
+ 	if (unlikely(nf_flow_exceeds_mtu(skb, flow->tuplehash[dir].tuple.mtu)))
+ 		return NF_ACCEPT;
+ 
++	if (nf_flow_tcp_state_check(flow, skb, sizeof(*ip6h)))
++		return NF_ACCEPT;
++
+ 	if (skb_try_make_writable(skb, sizeof(*ip6h)))
+ 		return NF_DROP;
+