man: ip-link.8: add a note for gso_ipv4_max_size

As Paolo noticed, a skb->len check against gso_max_size was added in:

  https://lore.kernel.org/netdev/20231219125331.4127498-1-edumazet@google.com/

gso_max_size needs to be set to a value greater than or equal to
gso_ipv4_max_size to make BIG TCP IPv4 work properly.

To not break the current setup, this patch just adds a note into its
man doc for this.

Reported-by: Xiumei Mu <xmu@redhat.com>
Signed-off-by: Xin Long <lucien.xin@gmail.com>

diff --git a/man/man8/ip-link.8.in b/man/man8/ip-link.8.in
index dd686ae1523a49155cf3d242a4267f1888530701..31e2d7f0f5b81cb6bf23092db69407fc43711b2f 100644 (file)
--- a/man/man8/ip-link.8.in
+++ b/man/man8/ip-link.8.in
@@ -445,6 +445,11 @@ TCP for IPv6 on this device when the size is greater than 65536.
 specifies the recommended maximum size of a IPv4 Generic Segment Offload
 packet the new device should accept. This is especially used to enable
 BIG TCP for IPv4 on this device by setting to a size greater than 65536.
+Note that
+.B gso_max_size
+needs to be set to a size greater than or equal to
+.B gso_ipv4_max_size
+to really enable BIG TCP for IPv4.
 
 .TP
 .BI gso_max_segs " SEGMENTS "