[PATCH 12/18] conf: Move check for mapping port 0 to caller

[David Gibson <david@gibson.dropbear.id.au>]

conf_ports_range_except() checks that it hasn't been asked to map port 0,
which generally won't work.  However, there's only one callsite that
doesn't statically pass a non-zero value here.  Change the check to an
assert() and move the actual error message to that callsite.  This will
allow further cleanups later.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
---
 conf.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/conf.c b/conf.c
index e5baf8ee..dc9468c2 100644
--- a/conf.c
+++ b/conf.c
@@ -151,10 +151,7 @@ static void conf_ports_range_except(const struct ctx *c, char optname,
 	unsigned base, i;
 	uint8_t proto;
 
-	if (first == 0) {
-		die("Can't forward port 0 for option '-%c %s'",
-		    optname, optarg);
-	}
+	assert(first != 0);
 
 	if (optname == 't' || optname == 'T')
 		proto = IPPROTO_TCP;
@@ -404,6 +401,11 @@ static void conf_ports(const struct ctx *c, char optname, const char *optarg,
 		if ((*p != '\0')  && (*p != ',')) /* Garbage after the ranges */
 			goto bad;
 
+		if (orig_range.first == 0) {
+			die("Can't forward port 0 for option '-%c %s'",
+			    optname, optarg);
+		}
+
 		conf_ports_range_except(c, optname, optarg, fwd,
 					addr, ifname,
 					orig_range.first, orig_range.last,
-- 
2.53.0