netlink_delinarize: don't check for set element if set is not populated

0065_icmp_postprocessing: line 13: Segmentation fault $NFT insert rule ip x foo index 1 accept

Since no listing is done, cache isn't populated and 'nft insert' will trip over
set->init == NULL during postprocessing of the existing 'icmp id 42' expression.

Fixes: 9a5574e2d4e9 ("netlink_delinearize: add missing icmp id/sequence support")
Reported-by: Eric Garver <eric@garver.life>
Reported-by: Phil Sutter <phil@nwl.cc>
Signed-off-by: Florian Westphal <fw@strlen.de>

1 files changed, 13 insertions, 0 deletions

diff --git a/tests/shell/testcases/sets/0065_icmp_postprocessing b/tests/shell/testcases/sets/0065_icmp_postprocessing
new file mode 100755
index 00000000..f838c3ef
--- /dev/null
+++ b/tests/shell/testcases/sets/0065_icmp_postprocessing
@@ -0,0 +1,13 @@
+#!/bin/bash
+
+set -e
+
+RULESET="table ip x {
+	chain foo {
+		icmp id 42
+	}
+}"
+
+$NFT -f - <<< $RULESET
+
+$NFT insert rule ip x foo index 0 accept