[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 <eduma...@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