LU-18199 scripts: fix ksocklnd-config gateway selection logic

To avoid disruption of network connectivity during LNet start-up,
fix gateway selection logic in ksocklnd-config script to:
        1) select only pingable gateways
        2) prefer to select the gateway featured in the default route
           with the "dev" matching the interface being configured

Fixes: 7f60b2b55 ("LU-17006 lnet: set up routes for going across subnets")
Test-Parameters: trivial testlist=sanity-lnet
Signed-off-by: Serguei Smirnov <ssmirnov@whamcloud.com>
Change-Id: I7fdfcf2d7e9acae18e9a2efb34a58c17d2887683
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/56321
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Tested-by: Sebastien Buisson <sbuisson@ddn.com>
Tested-by: Cyril Bordage <cbordage@whamcloud.com>
Reviewed-by: Cyril Bordage <cbordage@whamcloud.com>
Reviewed-by: Frank Sehr <fsehr@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>

diff --git a/lustre/scripts/ksocklnd-config b/lustre/scripts/ksocklnd-config
index 31f281f..7db77b9 100755 (executable)
--- a/lustre/scripts/ksocklnd-config
+++ b/lustre/scripts/ksocklnd-config
@@ -249,17 +249,45 @@ do
        fi
 done
 
-# generate list of available default gateways
-gwsline=$(/sbin/ip route | awk '/default/ { print $3 }')
-gateways=($gwsline)
-
-gwsline_ipv6=$(/sbin/ip -6 route | awk '/default/ { print $3 }')
-gateways_ipv6=($gwsline_ipv6)
+# generate list of available not-dev-specific default gateways
+gwsline=$(/sbin/ip route | awk '/default/ { if ($0 !~ /dev/) print $3 }')
+comm_gateways=($gwsline)
+
+gwsline_ipv6=$(/sbin/ip -6 route | awk '/default/ { if ($0 !~ /dev/) print $3 }')
+comm_gateways_ipv6=($gwsline_ipv6)
+
+# Ping the gw to check if it is alive
+pinggw() {
+       local gw=$1
+       local timeout=1  # Set the timeout for the ping command
+
+       # Determine if the IP is IPv4 or IPv6
+       if [[ $gw =~ .*:.* ]]; then
+               # IPv6: Use ping6
+               if ping6 -c 1 -W $timeout "$gw" &> /dev/null; then
+                       return 0  # reachable
+               else
+                       logcmd=(logger "${me}: unreachable default gateway ${gw}: skipping ")
+                       eval "${logcmd[@]}"
+                       return 1  # not reachable
+               fi
+       else
+               # IPv4: Use the standard ping
+               if ping -c 1 -W $timeout "$gw" &> /dev/null; then
+                       return 0  # reachable
+               else
+                       logcmd=(logger "${me}: unreachable default gateway ${gw}: skipping ")
+                       eval "${logcmd[@]}"
+                       return 1  # not reachable
+               fi
+       fi
+}
 
 # Select a gateway on the same subnet for both IPv4 and IPv6
 selectgw() {
        local ip=$1
        local mask=$2
+       local interface=$3
 
        # Check if the IP address is IPv4 or IPv6
        if [[ $ip =~ .*:.* ]]; then
@@ -279,11 +307,24 @@ selectgw() {
                done
 
                local network_ipv6=$result
-               for gw in "${gateways_ipv6[@]}"; do
+               local spec_gateways_ipv6=($(/sbin/ip -6 route show dev $interface | awk '/default/ { print $3 }'))
+
+               for gw in "${spec_gateways_ipv6[@]}"; do
                        gw_network=$(netcalcipv6 "$gw" "$mask")
                        if [[ "$network_ipv6" == "$gw_network" ]]; then
-                               echo $gw
-                               return
+                               if pinggw "$gw"; then
+                                       echo $gw
+                                       return
+                               fi
+                       fi
+               done
+               for gw in "${comm_gateways_ipv6[@]}"; do
+                       gw_network=$(netcalcipv6 "$gw" "$mask")
+                       if [[ "$network_ipv6" == "$gw_network" ]]; then
+                               if pinggw "$gw"; then
+                                       echo $gw
+                                       return
+                               fi
                        fi
                done
        else
@@ -298,11 +339,24 @@ selectgw() {
                        [ $i -lt 3 ] && network_ipv4+="."
                done
 
-               for gw in "${gateways[@]}"; do
+               local spec_gateways=($(/sbin/ip route show dev $interface | awk '/default/ { print $3 }'))
+
+               for gw in "${spec_gateways[@]}"; do
+                       gw_network=$(netcalc "$gw" "$mask")
+                       if [[ "$network_ipv4" == "$gw_network" ]]; then
+                               if pinggw "$gw"; then
+                                       echo $gw
+                                       return
+                               fi
+                       fi
+               done
+               for gw in "${comm_gateways[@]}"; do
                        gw_network=$(netcalc "$gw" "$mask")
                        if [[ "$network_ipv4" == "$gw_network" ]]; then
-                               echo $gw
-                               return
+                               if pinggw "$gw"; then
+                                       echo $gw
+                                       return
+                               fi
                        fi
                done
        fi
@@ -322,7 +376,7 @@ do
                # Convert CIDR mask to mask in dot format for IPv4
                dotmask_ipv4=$(cidr2mask ${cidrmask_ipv4[0]})
                # Find a gateway on the same subnet for IPv4
-               gw_ipv4=$(selectgw "${addr_ipv4[0]}" "$dotmask_ipv4")
+               gw_ipv4=$(selectgw "${addr_ipv4[0]}" "$dotmask_ipv4" "$i")
                # Build and execute route commands for IPv4
                if [[ $gw_ipv4 == "0.0.0.0" ]]; then
                        # Gateway not found, assume local destinations for IPv4
@@ -352,7 +406,7 @@ do
                # Convert CIDR mask to mask in dot format for IPv6
                dotmask_ipv6=$(cidr2maskipv6 ${cidrmask_ipv6[0]})
                # Find a gateway on the same subnet for IPv6
-               gw_ipv6=$(selectgw "${addr_ipv6[0]}" "$dotmask_ipv6")
+               gw_ipv6=$(selectgw "${addr_ipv6[0]}" "$dotmask_ipv6" "$i")
                # Build and execute route commands for IPv6
                if [[ $gw_ipv6 == "0.0.0.0" ]]; then
                        # Gateway not found, assume local destinations for IPv6