[PATCH net] ipv6: tcp: enable flowlabel reflection in some RST packets

[PATCH net] ipv6: tcp: enable flowlabel reflection in some RST packets

[Eric Dumazet]

This extends commit 22b6722bfa59 ("ipv6: Add sysctl for per
namespace flow label reflection"), for some TCP RST packets.

When RST packets are sent because no socket could be found,
it makes sense to use flowlabel_reflect sysctl to decide
if a reflection of the flowlabel is requested.

Signed-off-by: Eric Dumazet <edumazet@google.com>
---
 net/ipv6/tcp_ipv6.c | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index beaf284563015ef0677c39fc056e6ecde3518920..07684f1e02f773a9d3e22a86ae4e7b853cc0b73e 100644
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -916,15 +916,17 @@ static void tcp_v6_send_response(const struct sock *sk, struct sk_buff *skb, u32
 static void tcp_v6_send_reset(const struct sock *sk, struct sk_buff *skb)
 {
 	const struct tcphdr *th = tcp_hdr(skb);
+	struct ipv6hdr *ipv6h = ipv6_hdr(skb);
 	u32 seq = 0, ack_seq = 0;
 	struct tcp_md5sig_key *key = NULL;
 #ifdef CONFIG_TCP_MD5SIG
 	const __u8 *hash_location = NULL;
-	struct ipv6hdr *ipv6h = ipv6_hdr(skb);
 	unsigned char newhash[16];
 	int genhash;
 	struct sock *sk1 = NULL;
 #endif
+	__be32 label = 0;
+	struct net *net;
 	int oif = 0;
 
 	if (th->rst)
@@ -936,6 +938,7 @@ static void tcp_v6_send_reset(const struct sock *sk, struct sk_buff *skb)
 	if (!sk && !ipv6_unicast_destination(skb))
 		return;
 
+	net = dev_net(skb_dst(skb)->dev);
 #ifdef CONFIG_TCP_MD5SIG
 	rcu_read_lock();
 	hash_location = tcp_parse_md5sig_option(th);
@@ -949,7 +952,7 @@ static void tcp_v6_send_reset(const struct sock *sk, struct sk_buff *skb)
 		 * Incoming packet is checked with md5 hash with finding key,
 		 * no RST generated if md5 hash doesn't match.
 		 */
-		sk1 = inet6_lookup_listener(dev_net(skb_dst(skb)->dev),
+		sk1 = inet6_lookup_listener(net,
 					   &tcp_hashinfo, NULL, 0,
 					   &ipv6h->saddr,
 					   th->source, &ipv6h->daddr,
@@ -979,9 +982,13 @@ static void tcp_v6_send_reset(const struct sock *sk, struct sk_buff *skb)
 		oif = sk->sk_bound_dev_if;
 		if (sk_fullsock(sk))
 			trace_tcp_send_reset(sk, skb);
+	} else {
+		if (net->ipv6.sysctl.flowlabel_reflect)
+			label = ip6_flowlabel(ipv6h);
 	}
 
-	tcp_v6_send_response(sk, skb, seq, ack_seq, 0, 0, 0, oif, key, 1, 0, 0);
+	tcp_v6_send_response(sk, skb, seq, ack_seq, 0, 0, 0, oif, key, 1, 0,
+			     label);
 
 #ifdef CONFIG_TCP_MD5SIG
 out:
-- 
2.22.0.rc1.311.g5d7573a151-goog

Re: [PATCH net] ipv6: tcp: enable flowlabel reflection in some RST packets

[Eric Dumazet]

On 6/4/19 12:29 PM, Eric Dumazet wrote:
> This extends commit 22b6722bfa59 ("ipv6: Add sysctl for per
> namespace flow label reflection"), for some TCP RST packets.
> 
> When RST packets are sent because no socket could be found,
> it makes sense to use flowlabel_reflect sysctl to decide
> if a reflection of the flowlabel is requested.
> 
> Signed-off-by: Eric Dumazet <edumazet@google.com>

Please wait for a V2, I will use another bit from the sysctl to limit the
risk of regressions.

Re: [PATCH net] ipv6: tcp: enable flowlabel reflection in some RST packets

[David Miller]

From: Eric Dumazet <eric.dumazet@gmail.com>
Date: Tue, 4 Jun 2019 18:16:00 -0700

> On 6/4/19 12:29 PM, Eric Dumazet wrote:
>> This extends commit 22b6722bfa59 ("ipv6: Add sysctl for per
>> namespace flow label reflection"), for some TCP RST packets.
>> 
>> When RST packets are sent because no socket could be found,
>> it makes sense to use flowlabel_reflect sysctl to decide
>> if a reflection of the flowlabel is requested.
>> 
>> Signed-off-by: Eric Dumazet <edumazet@google.com>
> 
> Please wait for a V2, I will use another bit from the sysctl to limit the
> risk of regressions.

Ok.