system/iptables: avoid trap when run "iptables -L" if configured CONF…

[masc2008]

avoid trap when run "iptables -L" if configured CONFIG_NET_NAT while not configured CONFIG_NET_IPFILTER
It's a trap happen everytime.

It's a trap happen everytime.

it can fix issue: #3294

[masc2008]

[BUG] trap when run "iptables -L" if configured CONFIG_NET_NAT while not configure CONFIG_NET_IPFILTER #3294 #3294

[xiaoxiang781216]

@masc2008 please fix:

../nuttx/tools/checkpatch.sh -c -u -m -g 85539a1223c4770ee36e68817f5bfe91e6b49369..HEAD
❌ Commit subject too long > 80
❌ Missing Signed-off-by
Used config files:
    1: .codespellrc
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[masc2008]

updated the commit info, please further review.

[hartmannathan]

Just to make sure I understand correctly: If args.table is NULL, it's OK to call iptables_apply()? Note that in iptables_apply(), COMMAND_FLUSH, COMMAND_LIST, and COMMAND_POLICY will try to access args->table. It's possible other commands also will try, but I didn't dig further. If this was unintended, the line could be changed as follows, which will prevent calling iptables_apply() if args.table is NULL.

Suggested change

	if (args.table == NULL || strcmp(args.table, TABLE_NAME_NAT) == 0)
	if (args.table != NULL && strcmp(args.table, TABLE_NAME_NAT) == 0)

[masc2008]

this will be more near to the standard behavior, thanks!