tcp: Apply device TSO segment limit earlier

Cache the device gso_max_segs in sock::sk_gso_max_segs and use it to
limit the size of TSO skbs.  This avoids the need to fall back to
software GSO for local TCP senders.

Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/core/sock.c b/net/core/sock.c
index 6b654b3..8f67ced 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -1458,6 +1458,7 @@
 		} else {
 			sk->sk_route_caps |= NETIF_F_SG | NETIF_F_HW_CSUM;
 			sk->sk_gso_max_size = dst->dev->gso_max_size;
+			sk->sk_gso_max_segs = dst->dev->gso_max_segs;
 		}
 	}
 }