dropbear: increase default receive window size

Increasing the receive window size improves throughout on higher-latency
links such as WAN connections. The current default of 24KB caps out at
around 500 KB/s.

Increasing the receive buffer to 256KB increases the throughput to at
least 11 MB/s.

Signed-off-by: David Bauer <mail@david-bauer.net>
(cherry picked from commit f95eecfb21ff08662e022accd30e8254028ff63b)

diff --git a/package/network/services/dropbear/files/dropbear.init b/package/network/services/dropbear/files/dropbear.init
index b82e967cbcedc4564dba6cfccc1383f7b7fa499f..a40b5f7baeea0f3a1e258f1a74aba0eb1ca3adcb 100755 (executable)
--- a/package/network/services/dropbear/files/dropbear.init
+++ b/package/network/services/dropbear/files/dropbear.init
@@ -155,6 +155,12 @@ dropbear_instance()
        PIDCOUNT="$(( ${PIDCOUNT} + 1))"
        local pid_file="/var/run/${NAME}.${PIDCOUNT}.pid"
 
+       # Increase default receive window size to increase
+       # throughput on high latency links
+       if [ "${RecvWindowSize}" -eq "0" ]; then
+               RecvWindowSize="262144"
+       fi
+
        procd_open_instance
        procd_set_param command "$PROG" -F -P "$pid_file"
        [ "${PasswordAuth}" -eq 0 ] && procd_append_param command -s