tcp_bbr: better deal with suboptimal GSO (II)

This is second part of dealing with suboptimal device gso parameters.
In first patch (350c9f484bde "tcp_bbr: better deal with suboptimal GSO")
we dealt with devices having low gso_max_segs

Some devices lower gso_max_size from 64KB to 16 KB (r8152 is an example)

In order to probe an optimal cwnd, we want BBR being not sensitive
to whatever GSO constraint a device can have.

This patch removes tso_segs_goal() CC callback in favor of
min_tso_segs() for CC wanting to override sysctl_tcp_min_tso_segs

Next patch will remove bbr->tso_segs_goal since it does not have
to be persistent.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Acked-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 8 insertions, 7 deletions

diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 49d043de3476..383cac0ff0ec 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -1703,8 +1703,8 @@ static bool tcp_nagle_check(bool partial, const struct tcp_sock *tp,
 /* Return how many segs we'd like on a TSO packet,
  * to send one TSO packet per ms
  */
-u32 tcp_tso_autosize(const struct sock *sk, unsigned int mss_now,
-                     int min_tso_segs)
+static u32 tcp_tso_autosize(const struct sock *sk, unsigned int mss_now,
+                            int min_tso_segs)
 {
         u32 bytes, segs;
 
@@ -1720,7 +1720,6 @@ u32 tcp_tso_autosize(const struct sock *sk, unsigned int mss_now,
 
         return segs;
 }
-EXPORT_SYMBOL(tcp_tso_autosize);
 
 /* Return the number of segments we want in the skb we are transmitting.
  * See if congestion control module wants to decide; otherwise, autosize.
@@ -1728,11 +1727,13 @@ EXPORT_SYMBOL(tcp_tso_autosize);
 static u32 tcp_tso_segs(struct sock *sk, unsigned int mss_now)
 {
         const struct tcp_congestion_ops *ca_ops = inet_csk(sk)->icsk_ca_ops;
-        u32 tso_segs = ca_ops->tso_segs_goal ? ca_ops->tso_segs_goal(sk) : 0;
+        u32 min_tso, tso_segs;
 
-        if (!tso_segs)
-                tso_segs = tcp_tso_autosize(sk, mss_now,
-                                sock_net(sk)->ipv4.sysctl_tcp_min_tso_segs);
+        min_tso = ca_ops->min_tso_segs ?
+                        ca_ops->min_tso_segs(sk) :
+                        sock_net(sk)->ipv4.sysctl_tcp_min_tso_segs;
+
+        tso_segs = tcp_tso_autosize(sk, mss_now, min_tso);
         return min_t(u32, tso_segs, sk->sk_gso_max_segs);
 }