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Message-Id: <1414757602-27637-3-git-send-email-fw@strlen.de>
Date: Fri, 31 Oct 2014 13:13:22 +0100
From: Florian Westphal <fw@...len.de>
To: <netdev@...r.kernel.org>
Cc: Florian Westphal <fw@...len.de>,
Daniel Borkmann <dborkman@...hat.com>
Subject: [PATCH -next v2 2/2] net: allow setting ecn via routing table
Allows to set ECN on a per-route basis in case the sysctl tcp_ecn is not set to 1.
IOW, when ECN is set for specific routes, it provides a tcp_ecn=1 behaviour for that
route while the rest of the stack acts according to the global settings.
Having a more fine-grained per-route setting can be beneficial for various reasons,
for example a) within data centers, or b) local ISPs may deploy ECN support for
their own video/streaming services [1], etc.
One can use 'ip route change dev $dev $net features ecn' to toggle this.
[1] http://www.ietf.org/proceedings/89/slides/slides-89-tsvarea-1.pdf, p.15
Joint work with Daniel Borkmann.
Reference: http://thread.gmane.org/gmane.linux.network/335797
Suggested-by: Hannes Frederic Sowa <hannes@...essinduktion.org>
Signed-off-by: Daniel Borkmann <dborkman@...hat.com>
Signed-off-by: Florian Westphal <fw@...len.de>
---
Changes since v1:
reword commit message and add reference to the discussion of the v1 patchset
net/ipv4/tcp_input.c | 25 +++++++++++++++----------
net/ipv4/tcp_output.c | 12 ++++++++++--
2 files changed, 25 insertions(+), 12 deletions(-)
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 4e4617e..9db942a 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -5876,20 +5876,22 @@ static inline void pr_drop_req(struct request_sock *req, __u16 port, int family)
*/
static void tcp_ecn_create_request(struct request_sock *req,
const struct sk_buff *skb,
- const struct sock *listen_sk)
+ const struct sock *listen_sk,
+ struct dst_entry *dst)
{
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;
+ bool ect, need_ecn, ecn_ok;
if (!th_ecn)
return;
ect = !INET_ECN_is_not_ect(TCP_SKB_CB(skb)->ip_dsfield);
need_ecn = tcp_ca_needs_ecn(listen_sk);
+ ecn_ok = net->ipv4.sysctl_tcp_ecn || dst_feature(dst, RTAX_FEATURE_ECN);
- if (!ect && !need_ecn && net->ipv4.sysctl_tcp_ecn)
+ if (!ect && !need_ecn && ecn_ok)
inet_rsk(req)->ecn_ok = 1;
else if (ect && need_ecn)
inet_rsk(req)->ecn_ok = 1;
@@ -5954,13 +5956,7 @@ int tcp_conn_request(struct request_sock_ops *rsk_ops,
if (security_inet_conn_request(sk, skb, req))
goto drop_and_free;
- if (!want_cookie || tmp_opt.tstamp_ok)
- tcp_ecn_create_request(req, skb, sk);
-
- if (want_cookie) {
- isn = cookie_init_sequence(af_ops, sk, skb, &req->mss);
- req->cookie_ts = tmp_opt.tstamp_ok;
- } else if (!isn) {
+ if (!want_cookie && !isn) {
/* VJ's idea. We save last timestamp seen
* from the destination in peer table, when entering
* state TIME-WAIT, and check against it before
@@ -6008,6 +6004,15 @@ int tcp_conn_request(struct request_sock_ops *rsk_ops,
goto drop_and_free;
}
+ tcp_ecn_create_request(req, skb, sk, dst);
+
+ if (want_cookie) {
+ isn = cookie_init_sequence(af_ops, sk, skb, &req->mss);
+ req->cookie_ts = tmp_opt.tstamp_ok;
+ if (!tmp_opt.tstamp_ok)
+ inet_rsk(req)->ecn_ok = 0;
+ }
+
tcp_rsk(req)->snt_isn = isn;
tcp_openreq_init_rwin(req, sk, dst);
fastopen = !want_cookie &&
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 3af2129..b1c6296 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -333,10 +333,18 @@ static void tcp_ecn_send_synack(struct sock *sk, struct sk_buff *skb)
static void tcp_ecn_send_syn(struct sock *sk, struct sk_buff *skb)
{
struct tcp_sock *tp = tcp_sk(sk);
+ bool use_ecn = sock_net(sk)->ipv4.sysctl_tcp_ecn == 1 ||
+ tcp_ca_needs_ecn(sk);
+
+ if (!use_ecn) {
+ const struct dst_entry *dst = __sk_dst_get(sk);
+ if (dst && dst_feature(dst, RTAX_FEATURE_ECN))
+ use_ecn = true;
+ }
tp->ecn_flags = 0;
- if (sock_net(sk)->ipv4.sysctl_tcp_ecn == 1 ||
- tcp_ca_needs_ecn(sk)) {
+
+ if (use_ecn) {
TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_ECE | TCPHDR_CWR;
tp->ecn_flags = TCP_ECN_OK;
if (tcp_ca_needs_ecn(sk))
--
2.0.4
--
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