Reduce network device speed to 10M for WoL

In previous Arch/kernel versions, the network device speed was
automatically set to the lowest possible upon poweroff when WoL was
enabled.

Latest versions do keep the network device to its standard speed (1000M
for example), which consumes some useless power when computer is powered
off and WoL enabled.

Force speed lowering for WoL.
But restore it before continuing boot, when devices are unlocked,
otherwise it remains as-is.

Make it an option, to select the wanted speed, or leave it as-is.

README.md

@@ -52,6 +52,12 @@ Some options can be set in `/etc/initcpio/sshcs_env` (file is sourced in initram
       - default: `g` (MagicPacket™)
       - usually WoL is disabled once in initramfs shell
       - set empty to not change network device WoL setting
+   * `sshcs_opt_net_speed`: speed to set on network device
+      - default: `10`
+      - full duplex is enabled, and auto-negociation disabled
+      - latest Arch/kernel tend to keep the speed at 1000M even during WoL
+      - this only applies to boot phase and persists for WoL: when unlocking devices, the network is reconfigured before the OS is fully ready
+      - set `0` to not change network device speed
    * `sshcs_opt_timeout_ipconfig`: time (in seconds) to configure IP
       - default: `10`
    * `sshcs_opt_listen`: SSH listening port

src/hooks/ssh-cryptsetup

@@ -18,6 +18,8 @@ sshcs_net_start() {
     return 1
   }
 
+  # Note: ethtool can access WoL settings right now, but not other settings
+  # until the network is setup.
   if [ "${sshcs_opt_net_wol:-d}" != "d" ]; then
     log_dbg "Setting network device=${net_device} wol=${sshcs_opt_net_wol}"
     ethtool -s "${net_device}" wol "${sshcs_opt_net_wol}"
@@ -60,7 +62,15 @@ sshcs_net_start() {
 
   log_msg "IP-Config: device=${net_device} ip=${net_address}/${net_netmask} gw=${net_gateway} dns0=${net_dns0} dns1=${net_dns1}"
 
-  [ -n "${net_address}" ]
+  # Ensure we have an address
+  [ -n "${net_address}" ] || return 1
+
+  # Note: We cannot change the device settings, other than WoL, before the
+  # network is setup.
+  if [ ${sshcs_opt_net_speed} != 0 ]; then
+    log_dbg "Setting network device=${net_device} speed=${sshcs_opt_net_speed}"
+    ethtool -s "${net_device}" speed "${sshcs_opt_net_speed}" duplex full autoneg off
+  fi
 }
 
 sshcs_net_done() {

src/hooks/ssh-cryptsetup-tools

@@ -33,6 +33,7 @@ sshcs_env_load() {
   local log_kmsg_default=1
   local debug_default=0
   local net_wol_default=g
+  local net_speed_default=10
   local timeout_ipconfig_default=10
   local timeout_poweroff_min=120
   local use_shell_default=0
@@ -43,6 +44,7 @@ sshcs_env_load() {
   [ -z "${sshcs_opt_log_kmsg}" ] && sshcs_opt_log_kmsg=${log_kmsg_default}
   [ -z "${sshcs_opt_debug}" ] && sshcs_opt_debug=${debug_default}
   [ -z "${sshcs_opt_net_wol}" ] && sshcs_opt_net_wol=${net_wol_default}
+  [ -z "${sshcs_opt_net_speed}" ] && sshcs_opt_net_speed=${net_speed_default}
   [ -z "${sshcs_opt_timeout_ipconfig}" ] && sshcs_opt_timeout_ipconfig=${timeout_ipconfig_default}
   [ -n "${sshcs_opt_listen}" ] && sshcs_opt_listen="-p ${sshcs_opt_listen}"
   [ -z "${sshcs_opt_timeout_poweroff}" ] && sshcs_opt_timeout_poweroff=${timeout_poweroff_min}
@@ -104,6 +106,12 @@ sshcs_cleanup() {
   # Thus as long as all devices have been unlocked, we don't expect any script
   # to be stuck on 'cryptsetup' calls.
 
+  # If we did change the network speed, time to reset it.
+  if [ -n "${net_device}" ] && [ ${sshcs_opt_net_speed} != 0 ]; then
+    log_dbg "Restoring network device=${net_device} speed"
+    ethtool -s "${net_device}" autoneg on
+  fi
+
   if proc_is_console; then
     # We are in the console.
     # It is time to properly end the processes we started and files we created.