[PATCH v3] save exact route to remote target

[Baoquan He]

Previously for solving static route issues, all routes which go
through a specific dev will be saved in 1st kernel, and then added
in 2nd kernel. Because we use below search pattern, an exception
will happen:
/sbin/ip route show | grep -v default | grep "^[[:digit:]].*via.* $_netdev"

That exception is a corner case which happened when 2 machines connected
directly by cable and the 2 network interfaces are configured in
different network subnets. E.g there are 2 machines A and B:

A:ens10 < ------ > B:ens9

A:ens10  inet 192.168.100.111/24 scope global ens10
route need be added in A:
192.168.110.0/24 dev ens10

B:ens9   inet 192.168.110.222/24 scope global ens9
route need be added in B
192.168.100.0/24 dev ens9

Now if A want to dump to B, the route "192.168.110.0/24 dev ens10"
has to be saved and added in 2nd kernel.

So in this patch "ip route get to $target" command is executed, then
an exact route can be got for going to that target. By this, static
route works and the corner case can be fixed too.

Signed-off-by: Baoquan He <bhe(a)redhat.com&gt;
---
 dracut-module-setup.sh | 31 +++++++++++++++++++++++--------
 1 file changed, 23 insertions(+), 8 deletions(-)

diff --git a/dracut-module-setup.sh b/dracut-module-setup.sh
index 02a0557..9da1a41 100755
--- a/dracut-module-setup.sh
+++ b/dracut-module-setup.sh
@@ -79,11 +79,6 @@ kdump_static_ip() {
        _gateway=$(ip route list dev $_netdev | awk '/^default /{print $3}')
        echo -n "${_srcaddr}::${_gateway}:${_netmask}::"
     fi
-
-    /sbin/ip route show | grep -v default | grep "^[[:digit:]].*via.* $_netdev
" |\
-    while read line; do
-        echo $line | awk '{printf("rd.route=%s:%s:%s\n", $1, $3, $5)}'
-    done >> ${initdir}/etc/cmdline.d/45route-static.conf
 }
 
 kdump_get_mac_addr() {
@@ -212,9 +207,27 @@ kdump_setup_znet() {
     echo rd.znet=${NETTYPE},${SUBCHANNELS}${_options} >
${initdir}/etc/cmdline.d/30znet.conf
 }
 
+get_routes() {
+    local _netdev="$1" _target="$2"
+    local _route
+
+    _route=`/sbin/ip route get to $_target 2>&1`
+    if /sbin/ip route get to $_target | grep "via";
+    then
+        # route going to a different subnet via a router
+        echo $_route | awk '{printf("rd.route=%s:%s:%s\n", $1, $3,
$5)}' \
+            >> ${initdir}/etc/cmdline.d/45route-static.conf
+    else
+        # route going to a different subnet though directly connected
+        echo $_route | awk '{printf("rd.route=%s::%s\n", $1, $3)}' \
+            >> ${initdir}/etc/cmdline.d/45route-static.conf
+    fi
+
+}
+
 # Setup dracut to bringup a given network interface
 kdump_setup_netdev() {
-    local _netdev=$1 _srcaddr=$2
+    local _netdev=$1 _srcaddr=$2 _target=$3
     local _static _proto _ip_conf _ip_opts _ifname_opts
 
     if [ "$(uname -m)" = "s390x" ]; then
@@ -229,6 +242,8 @@ kdump_setup_netdev() {
         _proto=dhcp
     fi
 
+    get_routes $_netdev $_target
+
     _ip_conf="${initdir}/etc/cmdline.d/40ip.conf"
     _ip_opts=" ip=${_static}$(kdump_setup_ifname $_netdev):${_proto}"
 
@@ -281,7 +296,7 @@ kdump_install_net() {
         _netdev=`echo $_netdev|awk '{print $3}'|head -n 1`
     fi
 
-    kdump_setup_netdev "${_netdev}" "${_srcaddr}"
+    kdump_setup_netdev "${_netdev}" "${_srcaddr}"
"${_server}"
 
     #save netdev used for kdump as cmdline
     # Whoever calling kdump_install_net() is setting up the default gateway,
@@ -439,7 +454,7 @@ kdump_setup_iscsi_device() {
     srcaddr=$(echo $netdev | awk '{ print $3; exit }')
     netdev=$(echo $netdev | awk '{ print $1; exit }')
 
-    kdump_setup_netdev $netdev $srcaddr
+    kdump_setup_netdev $netdev $srcaddr $tgt_ipaddr
 
     # prepare netroot= command line
     # FIXME: IPV6 addresses require explicit [] around $tgt_ipaddr
-- 
1.9.0