test-dhcp-option: add assert to check index is nonnegative

CID #1237623.

diff --git a/src/libsystemd-network/test-dhcp-option.c b/src/libsystemd-network/test-dhcp-option.c
index 6062a37dabc376631cdb984f8b61e6efd39e730b..bd448ff2b20dc868056d8c0378f9f146a5a1adef 100644 (file)
--- a/src/libsystemd-network/test-dhcp-option.c
+++ b/src/libsystemd-network/test-dhcp-option.c
@@ -130,6 +130,8 @@ static DHCPMessage *create_message(uint8_t *options, uint16_t optlen,
 
 static void test_ignore_opts(uint8_t *descoption, int *descpos, int *desclen)
 {
+        assert(*descpos >= 0);
+
         while (*descpos < *desclen) {
                 switch(descoption[*descpos]) {
                 case DHCP_OPTION_PAD: