[PATCH gwproxy v4 5/6] dnsparser: Transaction id creation is delegated to caller

[Ahmad Gani <reyuki@gnuweeb.org>]

It gives the caller more flexibility in handling DNS requests.

A single domain name lookup can have two responses: one for IPv4 and one
for IPv6. With this change, the caller may use the same txid for both queries,
making it easier to group related DNS responses.

Signed-off-by: Ahmad Gani <reyuki@gnuweeb.org>
---
 src/gwproxy/dnsparser.c | 7 +++++--
 src/gwproxy/dnsparser.h | 1 +
 2 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/src/gwproxy/dnsparser.c b/src/gwproxy/dnsparser.c
index 744dc61581ef..2d8af1da2893 100644
--- a/src/gwproxy/dnsparser.c
+++ b/src/gwproxy/dnsparser.c
@@ -65,9 +65,9 @@ static ssize_t calculate_question_len(uint8_t *in, size_t in_len)
 
 int serialize_answ(uint16_t txid, uint8_t *in, size_t in_len, gwdns_answ_data *out)
 {
-	size_t idx;
 	gwdns_header_pkt *hdr;
 	uint16_t raw_flags;
+	size_t idx;
 	int ret;
 
 	idx = sizeof(*hdr);
@@ -244,7 +244,10 @@ ssize_t construct_question(gwdns_question_part *question)
 	* the memset implicitly set opcode to OPCODE_QUERY
 	*/
 	memset(hdr, 0, sizeof(*hdr));
-	hdr->id = htons((uint16_t)rand());
+	/*
+	 * no need to htons, so no ntohs for comparison in serialize_answ.
+	 */
+	hdr->id = question->txid;
 	DNS_SET_RD(hdr->flags, true);
 	hdr->flags = htons(hdr->flags);
 	hdr->qdcount = htons(1);
diff --git a/src/gwproxy/dnsparser.h b/src/gwproxy/dnsparser.h
index 41048568240b..502281ad9d57 100644
--- a/src/gwproxy/dnsparser.h
+++ b/src/gwproxy/dnsparser.h
@@ -116,6 +116,7 @@ typedef struct {
 
 typedef struct {
 	uint8_t *dst_buffer;
+	uint16_t txid;
 	uint16_t type;
 	size_t dst_len;
 	const char *domain;
-- 
Ahmad Gani