tests: shell: Add tests for low level json import

Test "nft import vm json".

Basically it loads same set of rules by "nft -f" and "nft import vm json"
and prints differences (if any) in the ruleset listed by "nft list
ruleset" in each case.

For Example:
$ ./run-tests.sh testcases/import/vm_json_import_0

Signed-off-by: Shyam Saini <mayhs11saini@gmail.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

diff --git a/tests/shell/testcases/import/vm_json_import_0 b/tests/shell/testcases/import/vm_json_import_0
new file mode 100755 (executable)
index 0000000..dc367f6
--- /dev/null
+++ b/tests/shell/testcases/import/vm_json_import_0
@@ -0,0 +1,71 @@
+#!/bin/bash
+
+tmpfile=$(mktemp)
+
+if [ ! -w $tmpfile ] ; then
+       echo "Failed to create tmp file" >&2
+       exit 0
+fi
+
+trap "rm -rf $tmpfile" EXIT # cleanup if aborted
+
+RULESET="table ip mangle {
+       set blackhole {
+               type ipv4_addr
+               elements = { 192.168.1.4, 192.168.1.5 }
+       }
+
+       chain prerouting {
+               type filter hook prerouting priority 0; policy accept;
+               tcp dport { ssh, http } accept
+               ip saddr @blackhole drop
+               icmp type echo-request accept
+               iifname \"lo\" accept
+               icmp type echo-request counter packets 0 bytes 0
+               ct state established,related accept
+               tcp flags != syn counter packets 7 bytes 841
+               ip saddr 192.168.1.100 ip daddr 192.168.1.1 counter packets 0 bytes 0
+       }
+}
+table arp x {
+       chain y {
+               arp htype 22
+               arp ptype ip
+               arp operation != rrequest
+               arp operation { request, reply, rrequest, rreply, inrequest, inreply, nak }
+               arp hlen 33-45
+       }
+}
+table bridge x {
+       chain y {
+               type filter hook input priority 0; policy accept;
+               vlan id 4094
+               vlan id 4094 vlan cfi 0
+               vlan id 1 ip saddr 10.0.0.0/23 udp dport domain
+       }
+}
+table ip6 x {
+       chain y {
+               type nat hook postrouting priority 0; policy accept;
+               icmpv6 id 33-45
+               ip6 daddr fe00::1-fe00::200 udp dport domain counter packets 0 bytes 0
+               meta l4proto tcp masquerade to :1024
+               iifname \"wlan0\" ct state established,new tcp dport vmap { ssh : drop, 222 : drop } masquerade
+               tcp dport ssh ip6 daddr 1::2 ether saddr 00:0f:54:0c:11:04 accept
+               ip6 daddr fe00::1-fe00::200 udp dport domain counter packets 0 bytes 0 masquerade
+       }
+}"
+
+echo "$RULESET" > $tmpfile
+$NFT -f $tmpfile
+$NFT export vm json > $tmpfile
+$NFT flush ruleset
+cat $tmpfile | $NFT import vm json
+
+RESULT="$($NFT list ruleset)"
+
+
+if [ "$RULESET" != "$RESULT" ] ; then
+       DIFF="$(which diff)"
+       [ -x $DIFF ] && $DIFF -u <(echo "$RULESET") <(echo "$RESULT")
+fi