Instead of limiting the control channel TCP/UDP packet payload size at
'100 bytes + real control channel overhead' (~140 bytes ethernet payload),
increase the max TCP/UDP payload size to '1250 bytes - calculated overhead'
(~1210 bytes ethernet payload).
Note that this patch does *not* yield an optimal solution, but it is a
simple and rather safe change that will improve connection setup times
significantly.
v2: use the mininum value of --link-mtu and 1250 to give the user a way to
reduce control packet size if really needed.
Signed-off-by: Steffan Karger <stef...@karger.me>
---
src/openvpn/ssl.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/src/openvpn/ssl.c b/src/openvpn/ssl.c
index bc17fd0..e61e0aa 100644
--- a/src/openvpn/ssl.c
+++ b/src/openvpn/ssl.c
@@ -299,8 +299,9 @@ tls_init_control_channel_frame_parameters(const struct
frame *data_channel_frame
reliable_ack_adjust_frame_parameters (frame, CONTROL_SEND_ACK_MAX);
frame_add_to_extra_frame (frame, SID_SIZE + sizeof (packet_id_type));
- /* set dynamic link MTU to minimum value */
- frame_set_mtu_dynamic (frame, 0, SET_MTU_TUN);
+ /* set dynamic link MTU to cap control channel packets at 1250 bytes */
+ ASSERT (TUN_LINK_DELTA (frame) < min_int (frame->link_mtu, 1250));
+ frame->link_mtu_dynamic = min_int (frame->link_mtu, 1250) - TUN_LINK_DELTA
(frame);
}
void
--
2.1.4
