netfilter: nf_nat_h323: fix logical-not-parentheses warning

Clang produces the following warning:

net/ipv4/netfilter/nf_nat_h323.c:553:6: error:
logical not is only applied to the left hand side of this comparison
  [-Werror,-Wlogical-not-parentheses]
if (!set_h225_addr(skb, protoff, data, dataoff, taddr,
    ^
add parentheses after the '!' to evaluate the comparison first
add parentheses around left hand side expression to silence this warning

There's not necessarily a bug here, but it's cleaner to return early,
ex:

if (x)
  return
...

rather than:

if (x == 0)
  ...
else
  return

Also added a return code check that seemed to be missing in one
instance.
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

net/ipv4/netfilter/nf_nat_h323.c

@@ -252,16 +252,16 @@ static int nat_rtp_rtcp(struct sk_buff *skb, struct nf_conn *ct,
 	if (set_h245_addr(skb, protoff, data, dataoff, taddr,
 			  &ct->tuplehash[!dir].tuple.dst.u3,
 			  htons((port & htons(1)) ? nated_port + 1 :
-						    nated_port)) == 0) {
-		/* Save ports */
-		info->rtp_port[i][dir] = rtp_port;
-		info->rtp_port[i][!dir] = htons(nated_port);
-	} else {
+						    nated_port))) {
 		nf_ct_unexpect_related(rtp_exp);
 		nf_ct_unexpect_related(rtcp_exp);
 		return -1;
 	}
 
+	/* Save ports */
+	info->rtp_port[i][dir] = rtp_port;
+	info->rtp_port[i][!dir] = htons(nated_port);
+
 	/* Success */
 	pr_debug("nf_nat_h323: expect RTP %pI4:%hu->%pI4:%hu\n",
 		 &rtp_exp->tuple.src.u3.ip,
@@ -370,15 +370,15 @@ static int nat_h245(struct sk_buff *skb, struct nf_conn *ct,
 	/* Modify signal */
 	if (set_h225_addr(skb, protoff, data, dataoff, taddr,
 			  &ct->tuplehash[!dir].tuple.dst.u3,
-			  htons(nated_port)) == 0) {
-		/* Save ports */
-		info->sig_port[dir] = port;
-		info->sig_port[!dir] = htons(nated_port);
-	} else {
+			  htons(nated_port))) {
 		nf_ct_unexpect_related(exp);
 		return -1;
 	}
 
+	/* Save ports */
+	info->sig_port[dir] = port;
+	info->sig_port[!dir] = htons(nated_port);
+
 	pr_debug("nf_nat_q931: expect H.245 %pI4:%hu->%pI4:%hu\n",
 		 &exp->tuple.src.u3.ip,
 		 ntohs(exp->tuple.src.u.tcp.port),
@@ -462,7 +462,11 @@ static int nat_q931(struct sk_buff *skb, struct nf_conn *ct,
 	/* Modify signal */
 	if (set_h225_addr(skb, protoff, data, 0, &taddr[idx],
 			  &ct->tuplehash[!dir].tuple.dst.u3,
-			  htons(nated_port)) == 0) {
+			  htons(nated_port))) {
+		nf_ct_unexpect_related(exp);
+		return -1;
+	}
+
 	/* Save ports */
 	info->sig_port[dir] = port;
 	info->sig_port[!dir] = htons(nated_port);
@@ -471,14 +475,13 @@ static int nat_q931(struct sk_buff *skb, struct nf_conn *ct,
 	if (idx > 0 &&
 	    get_h225_addr(ct, *data, &taddr[0], &addr, &port) &&
 	    (ntohl(addr.ip) & 0xff000000) == 0x7f000000) {
-			set_h225_addr(skb, protoff, data, 0, &taddr[0],
+		if (set_h225_addr(skb, protoff, data, 0, &taddr[0],
 				  &ct->tuplehash[!dir].tuple.dst.u3,
-				      info->sig_port[!dir]);
-		}
-	} else {
+				  info->sig_port[!dir])) {
 			nf_ct_unexpect_related(exp);
 			return -1;
 		}
+	}
 
 	/* Success */
 	pr_debug("nf_nat_ras: expect Q.931 %pI4:%hu->%pI4:%hu\n",
@@ -550,9 +553,9 @@ static int nat_callforwarding(struct sk_buff *skb, struct nf_conn *ct,
 	}
 
 	/* Modify signal */
-	if (!set_h225_addr(skb, protoff, data, dataoff, taddr,
+	if (set_h225_addr(skb, protoff, data, dataoff, taddr,
 			  &ct->tuplehash[!dir].tuple.dst.u3,
-			   htons(nated_port)) == 0) {
+			  htons(nated_port))) {
 		nf_ct_unexpect_related(exp);
 		return -1;
 	}