dnsproxy: Use DNS header in checks

We should use the DNS header struct when checking DNS
protocol values instead of using pointer so that the
TCP offset is properly taken care of.

diff --git a/src/dnsproxy.c b/src/dnsproxy.c
index e7123f1..dc8ab13 100644 (file)
--- a/src/dnsproxy.c
+++ b/src/dnsproxy.c
@@ -1246,6 +1246,7 @@ static int cache_update(struct server_data *srv, unsigned char *msg,
        int offset = protocol_offset(srv->protocol);
        int err, qlen, ttl = 0;
        uint16_t answers = 0, type = 0, class = 0;
+       struct domain_hdr *hdr = (void *)(msg + offset);
        struct domain_question *q;
        struct cache_entry *entry;
        struct cache_data *data;
@@ -1270,12 +1271,13 @@ static int cache_update(struct server_data *srv, unsigned char *msg,
                next_refresh = current_time + 30;
        }
 
-
-       /* Continue only if response code is 0 (=ok) */
-       if (msg[3] & 0x0f)
+       if (offset < 0)
                return 0;
 
-       if (offset < 0)
+       DBG("offset %d hdr %p msg %p rcode %d", offset, hdr, msg, hdr->rcode);
+
+       /* Continue only if response code is 0 (=ok) */
+       if (hdr->rcode != 0)
                return 0;
 
        rsplen = sizeof(response) - 1;
@@ -1303,7 +1305,7 @@ static int cache_update(struct server_data *srv, unsigned char *msg,
                                return -ENOMEM;
                        data->inserted = entry->ipv4->inserted;
                        data->type = type;
-                       data->answers = msg[5];
+                       data->answers = hdr->ancount;
                        data->timeout = entry->ipv4->timeout;
                        if (srv->protocol == IPPROTO_UDP)
                                cache_offset = 2;