diff options
Diffstat (limited to 'net/ipv4/tcp_input.c')
| -rw-r--r-- | net/ipv4/tcp_input.c | 36 |
1 files changed, 35 insertions, 1 deletions
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c index fc133178c78..174181e28ef 100644 --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -5906,6 +5906,40 @@ static inline void pr_drop_req(struct request_sock *req, __u16 port, int family) #endif } +/* RFC3168 : 6.1.1 SYN packets must not have ECT/ECN bits set + * + * If we receive a SYN packet with these bits set, it means a + * network is playing bad games with TOS bits. In order to + * avoid possible false congestion notifications, we disable + * TCP ECN negociation. + * + * Exception: tcp_ca wants ECN. This is required for DCTCP + * congestion control; it requires setting ECT on all packets, + * including SYN. We inverse the test in this case: If our + * local socket wants ECN, but peer only set ece/cwr (but not + * ECT in IP header) its probably a non-DCTCP aware sender. + */ +static void tcp_ecn_create_request(struct request_sock *req, + const struct sk_buff *skb, + const struct sock *listen_sk) +{ + const struct tcphdr *th = tcp_hdr(skb); + const struct net *net = sock_net(listen_sk); + bool th_ecn = th->ece && th->cwr; + bool ect, need_ecn; + + if (!th_ecn) + return; + + ect = !INET_ECN_is_not_ect(TCP_SKB_CB(skb)->ip_dsfield); + need_ecn = tcp_ca_needs_ecn(listen_sk); + + if (!ect && !need_ecn && net->ipv4.sysctl_tcp_ecn) + inet_rsk(req)->ecn_ok = 1; + else if (ect && need_ecn) + inet_rsk(req)->ecn_ok = 1; +} + int tcp_conn_request(struct request_sock_ops *rsk_ops, const struct tcp_request_sock_ops *af_ops, struct sock *sk, struct sk_buff *skb) @@ -5966,7 +6000,7 @@ int tcp_conn_request(struct request_sock_ops *rsk_ops, goto drop_and_free; if (!want_cookie || tmp_opt.tstamp_ok) - TCP_ECN_create_request(req, skb, sk); + tcp_ecn_create_request(req, skb, sk); if (want_cookie) { isn = cookie_init_sequence(af_ops, sk, skb, &req->mss); |