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. The packet containing RST/FIN is also sent to the slow path
and the TCP conntrack module will update its state.

Signed-off-by: Felix Fietkau <nbd@nbd.name>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

diff --git a/net/netfilter/nf_flow_table_ip.c b/net/netfilter/nf_flow_table_ip.c
index dc570fb..692c75e 100644 (file)
--- 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)
 {
@@ -119,10 +136,9 @@ static int nf_flow_dnat_ip(const struct flow_offload *flow, struct sk_buff *skb,
 }
 
 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 ||
@@ -202,6 +218,7 @@ nf_flow_offload_ip_hook(void *priv, struct sk_buff *skb,
        struct flow_offload *flow;
        struct net_device *outdev;
        const struct rtable *rt;
+       unsigned int thoff;
        struct iphdr *iph;
        __be32 nexthop;
 
@@ -230,8 +247,12 @@ nf_flow_offload_ip_hook(void *priv, struct sk_buff *skb,
        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;
@@ -439,6 +460,9 @@ nf_flow_offload_ipv6_hook(void *priv, struct sk_buff *skb,
        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;