net/ipv4: disable SMC TCP option with SYN Cookies

Currently, the SMC experimental TCP option in a SYN packet is lost on
the server side when SYN Cookies are active. However, the corresponding
SYNACK sent back to the client contains the SMC option. This causes an
inconsistent view of the SMC capabilities on the client and server.

This patch disables the SMC option in the SYNACK when SYN Cookies are
active to avoid this issue.

Fixes: 60e2a7780793b ("tcp: TCP experimental option for SMC")
Signed-off-by: Hans Wippel <hwippel@linux.vnet.ibm.com>
Signed-off-by: Ursula Braun <ubraun@linux.vnet.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/ipv4/syncookies.c b/net/ipv4/syncookies.c
index fda37f2..c3387df 100644 (file)
--- a/net/ipv4/syncookies.c
+++ b/net/ipv4/syncookies.c
@@ -349,6 +349,8 @@ struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb)
        req->ts_recent          = tcp_opt.saw_tstamp ? tcp_opt.rcv_tsval : 0;
        treq->snt_synack        = 0;
        treq->tfo_listener      = false;
+       if (IS_ENABLED(CONFIG_SMC))
+               ireq->smc_ok = 0;
 
        ireq->ir_iif = inet_request_bound_dev_if(sk, skb);
 

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 9a1b3c1..ff6cd98 100644 (file)
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -6256,6 +6256,9 @@ int tcp_conn_request(struct request_sock_ops *rsk_ops,
        if (want_cookie && !tmp_opt.saw_tstamp)
                tcp_clear_options(&tmp_opt);
 
+       if (IS_ENABLED(CONFIG_SMC) && want_cookie)
+               tmp_opt.smc_ok = 0;
+
        tmp_opt.tstamp_ok = tmp_opt.saw_tstamp;
        tcp_openreq_init(req, &tmp_opt, skb, sk);
        inet_rsk(req)->no_srccheck = inet_sk(sk)->transparent;

diff --git a/net/ipv6/syncookies.c b/net/ipv6/syncookies.c
index e7a3a6b..e997141 100644 (file)
--- a/net/ipv6/syncookies.c
+++ b/net/ipv6/syncookies.c
@@ -217,6 +217,8 @@ struct sock *cookie_v6_check(struct sock *sk, struct sk_buff *skb)
        treq->snt_isn = cookie;
        treq->ts_off = 0;
        treq->txhash = net_tx_rndhash();
+       if (IS_ENABLED(CONFIG_SMC))
+               ireq->smc_ok = 0;
 
        /*
         * We need to lookup the dst_entry to get the correct window size.