2 files changed, 14 insertions, 3 deletions

diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index 3dfbc21e555a..44aef1c1f373 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -1364,6 +1364,10 @@ struct sock *tcp_v4_syn_recv_sock(struct sock *sk, struct sk_buff *skb,
         tcp_mtup_init(newsk);
         tcp_sync_mss(newsk, dst_mtu(dst));
         newtp->advmss = dst_metric(dst, RTAX_ADVMSS);
+        if (tcp_sk(sk)->rx_opt.user_mss &&
+            tcp_sk(sk)->rx_opt.user_mss < newtp->advmss)
+                newtp->advmss = tcp_sk(sk)->rx_opt.user_mss;
+
         tcp_initialize_rcv_mss(newsk);
 
 #ifdef CONFIG_TCP_MD5SIG
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 8f9793a37b61..c3d58ee3e16f 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -2232,6 +2232,7 @@ struct sk_buff *tcp_make_synack(struct sock *sk, struct dst_entry *dst,
         struct sk_buff *skb;
         struct tcp_md5sig_key *md5;
         __u8 *md5_hash_location;
+        int mss;
 
         skb = sock_wmalloc(sk, MAX_TCP_HEADER + 15, 1, GFP_ATOMIC);
         if (skb == NULL)
@@ -2242,13 +2243,17 @@ struct sk_buff *tcp_make_synack(struct sock *sk, struct dst_entry *dst,
 
         skb->dst = dst_clone(dst);
 
+        mss = dst_metric(dst, RTAX_ADVMSS);
+        if (tp->rx_opt.user_mss && tp->rx_opt.user_mss < mss)
+                mss = tp->rx_opt.user_mss;
+
         if (req->rcv_wnd == 0) { /* ignored for retransmitted syns */
                 __u8 rcv_wscale;
                 /* Set this up on the first call only */
                 req->window_clamp = tp->window_clamp ? : dst_metric(dst, RTAX_WINDOW);
                 /* tcp_full_space because it is guaranteed to be the first packet */
                 tcp_select_initial_window(tcp_full_space(sk),
-                        dst_metric(dst, RTAX_ADVMSS) - (ireq->tstamp_ok ? TCPOLEN_TSTAMP_ALIGNED : 0),
+                        mss - (ireq->tstamp_ok ? TCPOLEN_TSTAMP_ALIGNED : 0),
                         &req->rcv_wnd,
                         &req->window_clamp,
                         ireq->wscale_ok,
@@ -2258,8 +2263,7 @@ struct sk_buff *tcp_make_synack(struct sock *sk, struct dst_entry *dst,
 
         memset(&opts, 0, sizeof(opts));
         TCP_SKB_CB(skb)->when = tcp_time_stamp;
-        tcp_header_size = tcp_synack_options(sk, req,
-                                             dst_metric(dst, RTAX_ADVMSS),
+        tcp_header_size = tcp_synack_options(sk, req, mss,
                                              skb, &opts, &md5) +
                           sizeof(struct tcphdr);
 
@@ -2333,6 +2337,9 @@ static void tcp_connect_init(struct sock *sk)
         if (!tp->window_clamp)
                 tp->window_clamp = dst_metric(dst, RTAX_WINDOW);
         tp->advmss = dst_metric(dst, RTAX_ADVMSS);
+        if (tp->rx_opt.user_mss && tp->rx_opt.user_mss < tp->advmss)
+                tp->advmss = tp->rx_opt.user_mss;
+
         tcp_initialize_rcv_mss(sk);
 
         tcp_select_initial_window(tcp_full_space(sk),