conntrack: default to unspec family for dualstack setups

2bcbae4c14b2 ("conntrack: -f family filter does not work") restored the
fallback to IPv4 if -f is not specified, which was the original
behaviour.

This patch modifies the default to use the unspec family if -f is not
specified for the following ct commands:

- list
- update
- delete
- get

(these two commands below do not support for -f though, but in case this is
extended in the future to support it):

- flush
- event

The existing code that parses IPv4 and IPv6 addresses already infers the
family, which simplifies the introduction of this update.

The expect commands are not updated, they still require many mandatory
options for filtering.

This patch includes a few test updates too.

Based on patch from Mikhail Sennikovsky.

Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

3 files changed, 32 insertions, 3 deletions

diff --git a/src/conntrack.c b/src/conntrack.c
index a26fa60..db35b07 100644
--- a/src/conntrack.c
+++ b/src/conntrack.c
@@ -41,6 +41,7 @@
 #include "conntrack.h"
 
 #include <stdio.h>
+#include <assert.h>
 #include <getopt.h>
 #include <stdlib.h>
 #include <ctype.h>
@@ -2171,6 +2172,7 @@ nfct_filter_init(const int family)
 {
 	filter_family = family;
 	if (options & CT_OPT_MASK_SRC) {
+		assert(family != AF_UNSPEC);
 		if (!(options & CT_OPT_ORIG_SRC))
 			exit_error(PARAMETER_PROBLEM,
 			           "Can't use --mask-src without --src");
@@ -2178,6 +2180,7 @@ nfct_filter_init(const int family)
 	}
 
 	if (options & CT_OPT_MASK_DST) {
+		assert(family != AF_UNSPEC);
 		if (!(options & CT_OPT_ORIG_DST))
 			exit_error(PARAMETER_PROBLEM,
 			           "Can't use --mask-dst without --dst");
@@ -2574,9 +2577,22 @@ int main(int argc, char *argv[])
 		}
 	}
 
-	/* default family */
-	if (family == AF_UNSPEC)
-		family = AF_INET;
+	/* default family only for the following commands */
+	if (family == AF_UNSPEC) {
+		switch (command) {
+		case CT_LIST:
+		case CT_UPDATE:
+		case CT_DELETE:
+		case CT_GET:
+		case CT_FLUSH:
+		case CT_EVENT:
+			break;
+		default:
+			family = AF_INET;
+			break;
+		}
+	}
+
 
 	/* we cannot check this combination with generic_opt_check. */
 	if (options & CT_OPT_ANY_NAT &&
diff --git a/tests/conntrack/testsuite/01delete b/tests/conntrack/testsuite/01delete
index 2755491..64dbb10 100644
--- a/tests/conntrack/testsuite/01delete
+++ b/tests/conntrack/testsuite/01delete
@@ -30,3 +30,8 @@
 -D -s 1.1.1.0/24 -d 2.2.2.0/24 ; OK
 # try same command again but with CIDR (no matching found)
 -D -s 1.1.1.0/24 -d 2.2.2.0/24 ; BAD
+# try to delete mismatching address family
+-D -s ::1 -d 2.2.2.2 ; BAD
+# try to delete IPv6 address without specifying IPv6 family
+-I -s ::1 -d ::2 -p tcp --sport 20 --dport 10 --state LISTEN -u SEEN_REPLY -t 40 ; OK
+-D -s ::1 ; OK
diff --git a/tests/conntrack/testsuite/02filter b/tests/conntrack/testsuite/02filter
index 91a75eb..d58637f 100644
--- a/tests/conntrack/testsuite/02filter
+++ b/tests/conntrack/testsuite/02filter
@@ -23,5 +23,13 @@ conntrack -L --mark 0/0xffffffff; OK
 conntrack -L -s 1.1.1.0 --mask-src 255.255.255.0 -d 2.0.0.0 --mask-dst 255.0.0.0 ; OK
 conntrack -L -s 1.1.1.4/24 -d 2.3.4.5/8 ; OK
 conntrack -L -s 1.1.2.0/24 -d 2.3.4.5/8 ; OK
+# filter filter mismatching address family
+conntrack -L -s 2.2.2.2 -d ::1 ; BAD
+# filter by IPv6 address, it implicitly sets IPv6 family
+conntrack -L -s ::1 ; OK
+# filter by IPv6 address mask, it implicitly sets IPv6 family
+conntrack -L -s abcd:abcd:abcd:: --mask-src ffff:ffff:ffff:: ; OK
+# filter filter mismatching address family
+conntrack -L --mask-src ffff:ffff:ffff:: --mask-dst 255.0.0.0 ; BAD
 # delete dummy
 conntrack -D -d 2.2.2.2 ; OK