[PATCH v9 3/3] dracut-kdump.sh: cancel StrictHostKeyChecking for ssh in link local ipv6

[Ziyue Yang]

ssh target of link local ipv6 might have network interface
name prefixed by 'kdump-', which is not in known_hosts while
dumping, leading to failure in dump_ssh.

This commit
1) adds a helper function is_ipv6_link_local_ifname_prefixed
to find out whether a host is a link local ipv6 address
with 'kdump-' prefixed ifname;
2) makes dump_ssh cancel 'StrictHostKeyChecking' for link
local ipv6 address cases in order to bypass the known_hosts,
for it's not possible to add 'kdump-' variants in hashed
known_hosts if there is any need.

Signed-off-by: Ziyue Yang 
---
 dracut-kdump.sh | 10 +++++++++-
 kdump-lib.sh    |  8 ++++++++
 2 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/dracut-kdump.sh b/dracut-kdump.sh
index b75c2a5..2c32e4e 100755
--- a/dracut-kdump.sh
+++ b/dracut-kdump.sh
@@ -71,10 +71,18 @@ dump_raw()

dump_ssh()
 {
-    local _opt="-i $1 -o BatchMode=yes -o StrictHostKeyChecking=yes"
+    local _opt="-i $1 -o BatchMode=yes"
     local _dir="$KDUMP_PATH/$HOST_IP-$DATEDIR"
     local _host=$2

+    # cancel HostKeyChecking for link-local ipv6 address
+    # with "kdump-" prefixed interface name
+    if is_ipv6_link_local_ifname_prefixed $(get_remote_host $_host); then
+        _opt+=" -o StrictHostKeyChecking=no"
+    else
+        _opt+=" -o StrictHostKeyChecking=yes"
+    fi
+
     echo "kdump: saving to $_host:$_dir"

cat /var/lib/random-seed > /dev/urandom
diff --git a/kdump-lib.sh b/kdump-lib.sh
index fb3e354..06548fe 100755
--- a/kdump-lib.sh
+++ b/kdump-lib.sh
@@ -317,6 +317,14 @@ is_ipv6_link_local()
     echo $1 | grep -q "^fe80::"
 }

+is_ipv6_link_local_ifname_prefixed()
+{
+    is_ipv6_link_local $1 && {
+        local _postfix=${1##*%}
+        echo $_postfix | grep -q "^kdump-"
+    }
+}
+
 # get ip address or hostname from nfs/ssh config value
 get_remote_host()
 {