[PATCH gwproxy v1 2/2] add support for AAAA record type

[ReYuki <reyuki@gnuweeb.org>]

From: ReYuki <me@reyuki.site>

https://datatracker.ietf.org/doc/html/rfc3596
2.1 AAAA record type

   The AAAA resource record type is a record specific to the Internet
   class that stores a single IPv6 address.

   The IANA assigned value of the type is 28 (decimal).

the following is a sample from dig command (strace -x -s 512  dig A google.com):
// dns request query packet
// header section
\xfd\x11 // id
\x01\x20 // flags
\x00\x01 // qdcount
\x00\x00 // ancount
\x00\x00 // nscount
\x00\x01 // arcount

// question section
// name
\x06\x67\x6f\x6f\x67\x6c\x65
\x03\x63\x6f\x6d
\x00\x00 // type
\x1c\x00 // class

// additional resource section
\x01\x00\x00\x29\x04\xd0\x00\x00\x00\x00\x00\x0c\x00\x0a\x00\x08\x21\x06\x68\xe2\x80\xc2\xe8\xb8

// dns response answer packet
// header section
\xfd\x11 // id
\x81\x80 // flags
\x00\x01 // qdcount
\x00\x04 // ancount
\x00\x00 // nscount
\x00\x01 // arcount

// question section
\x06\x67\x6f\x6f\x67\x6c\x65
\x03\x63\x6f\x6d
\x00
\x00\x1c // type
\x00\x01 // class

// (1) answer section
\xc0\x0c // name
\x00\x1c // type
\x00\x01 // class
\x00\x00\x06\xd1 // ttl
\x00\x10 // rdlength
\x24\x04\x68\x00\x40\x03\x0c\x0f\x00\x00\x00\x00\x00\x00\x00\x8a // rdata

// (2) answer section
\xc0\x0c
\x00\x1c
\x00\x01
\x00\x00\x06\xd1
\x00\x10
\x24\x04\x68\x00\x40\x03\x0c\x0f\x00\x00\x00\x00\x00\x00\x00\x65

// (3) answer section
\xc0\x0c
\x00\x1c
\x00\x01
\x00\x00\x06\xd1
\x00\x10
\x24\x04\x68\x00\x40\x03\x0c\x0f\x00\x00\x00\x00\x00\x00\x00\x66

// (4) answer section
\xc0\x0c
\x00\x1c
\x00\x01
\x00\x00\x06\xd1
\x00\x10
\x24\x04\x68\x00\x40\x03\x0c\x0f\x00\x00\x00\x00\x00\x00\x00\x64

// additional resource section
\x00\x00\x29\x10\x00\x00\x00\x00\x00\x00\x00
---
 dnsclient.c      |  7 +++++--
 gwdnsparserlib.c | 14 +++++++++++++-
 gwdnsparserlib.h |  4 +++-
 3 files changed, 21 insertions(+), 4 deletions(-)

diff --git a/dnsclient.c b/dnsclient.c
index 4d96b18..6f2e66c 100644
--- a/dnsclient.c
+++ b/dnsclient.c
@@ -83,6 +83,7 @@ static int send_query(struct io_uring *ring, int sockfd, char *domain, gwdns_que
 	q.domain = domain;
 	q.dst_buffer = buff->question;
 	q.dst_len = UDP_MSG_LIMIT;
+	q.type = TYPE_AAAA;
 	payload_len = construct_question(&q);
 	if (payload_len < 0)
 		return -1;
@@ -161,13 +162,15 @@ static int resolv_addr(char **domains, gwdns_resolv_hint *hint, gwdns_resolv_ctx
 		ctx->sqe_nr--;
 		printf("cqe->res=%d cqe->user_data=%llx\n", cqe->res, CLEAR_ID(cqe->user_data));
 		if (EXTRACT_ID(cqe->user_data) == ID) {
-			char ipstr[INET_ADDRSTRLEN];
+			char ipstr[INET6_ADDRSTRLEN];
 			gwdns_answ_data d;
 
 			cqe->user_data = CLEAR_ID(cqe->user_data);
 			ret = serialize_answ((uint16_t)cqe->user_data, (uint8_t *)buff[idx].answr, cqe->res, &d);
 			for (size_t i = 0; i < d.hdr.ancount; i++) {
-				inet_ntop(AF_INET, d.rr_answ[i]->rdata, ipstr, sizeof(ipstr));
+				gwdns_serialized_answ *p = d.rr_answ[i];
+				int sa_family = p->rr_type == TYPE_AAAA ? AF_INET6 : AF_INET;
+				inet_ntop(sa_family, p->rdata, ipstr, sizeof(ipstr));
 				printf("%s\n", ipstr);
 			}
 			
diff --git a/gwdnsparserlib.c b/gwdnsparserlib.c
index aa883d9..022ccc2 100644
--- a/gwdnsparserlib.c
+++ b/gwdnsparserlib.c
@@ -1,3 +1,5 @@
+#define _DEFAULT_SOURCE
+#include <endian.h>
 #include "gwdnsparserlib.h"
 
 static ssize_t construct_qname(uint8_t *dst, size_t dst_len, const char *qname)
@@ -126,14 +128,21 @@ int serialize_answ(uint16_t txid, uint8_t *in, size_t in_len, gwdns_answ_data *o
 		in += 2; // NAME
 
 		memcpy(&item->rr_type, in, 2);
+		item->rr_type = ntohs(item->rr_type);
 		in += 2; // TYPE
 		memcpy(&item->rr_class, in, 2);
+		item->rr_class = ntohs(item->rr_class);
 		in += 2; // CLASS
 		memcpy(&item->ttl, in, 4);
+		item->ttl = be32toh(item->ttl);
 		in += 4; // TTL
 
 		memcpy(&rdlength, in, sizeof(rdlength));
 		rdlength = ntohs(rdlength);
+		if (item->rr_type == TYPE_AAAA && rdlength != sizeof(struct in6_addr))
+			return -EINVAL;
+		if (item->rr_type == TYPE_A && rdlength != sizeof(struct in_addr))
+			return -EINVAL;
 		item->rdlength = rdlength;
 		in += 2;
 
@@ -153,6 +162,9 @@ ssize_t construct_question(gwdns_question_part *question)
 	size_t required_len;
 	ssize_t bw;
 
+	if (question->type != TYPE_AAAA && question->type != TYPE_A)
+		return -EINVAL;
+
 	hdr = &pkt.hdr;
 	/*
 	* the memset implicitly set opcode to query
@@ -177,7 +189,7 @@ ssize_t construct_question(gwdns_question_part *question)
 		return bw;
 
 	pkt.body[bw++] = 0x0;
-	qtype = htons(TYPE_A);
+	qtype = htons(question->type);
 	qclass = htons(CLASS_IN);
 	memcpy(&pkt.body[bw], &qtype, 2);
 	bw += 2;
diff --git a/gwdnsparserlib.h b/gwdnsparserlib.h
index d24e414..c5948d0 100644
--- a/gwdnsparserlib.h
+++ b/gwdnsparserlib.h
@@ -91,6 +91,7 @@ typedef enum {
 	TYPE_MINFO	= 14,	// mailbox or mail list information
 	TYPE_MX		= 15,	// mail exchange
 	TYPE_TXT	= 16,	// text strings
+	TYPE_AAAA	= 28,	// text strings
 	QTYPE_AXFR	= 252,	// A request for a transfer of an entire zone
 	QTYPE_MAILB	= 253,	// A request for mailbox-related records (MB, MG or MR)
 	QTYPE_ALL	= 255	// A request for all records
@@ -119,6 +120,7 @@ typedef struct {
 
 typedef struct {
 	uint8_t *dst_buffer;
+	uint16_t type;
 	size_t dst_len;
 	char *domain;
 } gwdns_question_part;
@@ -190,7 +192,7 @@ typedef struct {
 * possible error are:
 * - ENAMETOOLONG	domain name in question.name is too long.
 * - ENOBUFS		length in question.dst_len is not sufficient.
-* - EINVAL		malformed question.name
+* - EINVAL		malformed or unsupported value in question data
 */
 ssize_t construct_question(gwdns_question_part *question);
 
-- 
ReYuki