netfilter: nf_nat: better error handling of nf_ct_expect_related() in helpers

This patch improves the situation in which the expectation table is
full for conntrack NAT helpers. Basically, we give up if we don't
find a place in the table instead of looping over nf_ct_expect_related()
with a different port (we should only do this if it returns -EBUSY, for
-EMFILE or -ESHUTDOWN I think that it's better to skip this).

Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Patrick McHardy <kaber@trash.net>

1 files changed, 23 insertions, 4 deletions

diff --git a/net/ipv4/netfilter/nf_nat_sip.c b/net/ipv4/netfilter/nf_nat_sip.c
index 11b538deaaec..e40cf7816fdb 100644
--- a/net/ipv4/netfilter/nf_nat_sip.c
+++ b/net/ipv4/netfilter/nf_nat_sip.c
@@ -307,9 +307,16 @@ static unsigned int ip_nat_sip_expect(struct sk_buff *skb, unsigned int dataoff,
 	exp->expectfn = ip_nat_sip_expected;
 
 	for (; port != 0; port++) {
+		int ret;
+
 		exp->tuple.dst.u.udp.port = htons(port);
-		if (nf_ct_expect_related(exp) == 0)
+		ret = nf_ct_expect_related(exp);
+		if (ret == 0)
+			break;
+		else if (ret != -EBUSY) {
+			port = 0;
 			break;
+		}
 	}
 
 	if (port == 0)
@@ -480,13 +487,25 @@ static unsigned int ip_nat_sdp_media(struct sk_buff *skb, unsigned int dataoff,
 	/* Try to get same pair of ports: if not, try to change them. */
 	for (port = ntohs(rtp_exp->tuple.dst.u.udp.port);
 	     port != 0; port += 2) {
+		int ret;
+
 		rtp_exp->tuple.dst.u.udp.port = htons(port);
-		if (nf_ct_expect_related(rtp_exp) != 0)
+		ret = nf_ct_expect_related(rtp_exp);
+		if (ret == -EBUSY)
 			continue;
+		else if (ret < 0) {
+			port = 0;
+			break;
+		}
 		rtcp_exp->tuple.dst.u.udp.port = htons(port + 1);
-		if (nf_ct_expect_related(rtcp_exp) == 0)
+		ret = nf_ct_expect_related(rtcp_exp);
+		if (ret == 0)
 			break;
-		nf_ct_unexpect_related(rtp_exp);
+		else if (ret != -EBUSY) {
+			nf_ct_unexpect_related(rtp_exp);
+			port = 0;
+			break;
+		}
 	}
 
 	if (port == 0)