add support for CAA lmao

src/dns.c

@@ -227,6 +227,72 @@ int dns_encode(char *buf, size_t buflen, struct query *q, qr_t qr,
 	return len;
 }
 
+/* Only used when iodined gets a CAA type query */
+/* Mostly same as dns_encode_ns_response() below */
+int dns_encode_caa_response(char *buf, size_t buflen, struct query *q,
+			   char *topdomain)
+{
+	HEADER *header;
+	int len;
+	short name;
+	int domain_len;
+	char *p;
+
+	if (buflen < sizeof(HEADER))
+		return 0;
+
+	memset(buf, 0, buflen);
+
+	header = (HEADER*)buf;
+
+	header->id = htons(q->id);
+	header->qr = 1;
+	header->opcode = 0;
+	header->aa = 1;
+	header->tc = 0;
+	header->rd = 0;
+	header->ra = 0;
+
+	p = buf + sizeof(HEADER);
+
+	header->qdcount = htons(1);
+	header->ancount = htons(1);
+
+	/* pointer to start of name */
+	name = 0xc000 | ((p - buf) & 0x3fff);
+
+	domain_len = strlen(q->name) - strlen(topdomain);
+	if (domain_len < 0 || domain_len == 1)
+		return -1;
+	if (strcasecmp(q->name + domain_len, topdomain))
+		return -1;
+	if (domain_len >= 1 && q->name[domain_len - 1] != '.')
+		return -1;
+
+	/* Query section */
+	putname(&p, buflen - (p - buf), q->name);	/* Name */
+	CHECKLEN(4);
+	putshort(&p, q->type);			/* Type */
+	putshort(&p, C_IN);			/* Class */
+
+	/* Answer section */
+	CHECKLEN(12);
+	putshort(&p, name);			/* Name */
+	putshort(&p, q->type);			/* Type */
+	putshort(&p, C_IN);			/* Class */
+	putlong(&p, 3600);			/* TTL */
+	putshort(&p, 22);			/* Data length */
+
+	/* caa record */
+	CHECKLEN(22);
+	memcpy(p, "\x00\x05\x69\x73\x73\x75\x65\x6c\x65\x74\x73\x65\x6e\x63\x72\x79\x70" \
+			"\x74\x2e\x6f\x72\x67", 22);
+	p += 22;
+
+	len = p - buf;
+	return len;
+}
+
 /* Only used when iodined gets an NS type query */
 /* Mostly same as dns_encode_a_response() below */
 int dns_encode_ns_response(char *buf, size_t buflen, struct query *q,

src/dns.h

@@ -28,6 +28,8 @@ typedef enum {
 extern int dnsc_use_edns0;
 
 int dns_encode(char *, size_t, struct query *, qr_t, const char *, size_t);
+int dns_encode_caa_response(char *buf, size_t buflen, struct query *q,
+			   char *topdomain);
 int dns_encode_ns_response(char *buf, size_t buflen, struct query *q,
 			   char *topdomain);
 int dns_encode_a_response(char *buf, size_t buflen, struct query *q);

src/iodined.c

@@ -1522,6 +1522,30 @@ handle_null_request(int tun_fd, int dns_fd, struct dnsfd *dns_fds, struct query
 	}
 }
 
+static void
+handle_caa_request(int dns_fd, struct query *q, int topdomain_offset)
+/* Mostly identical to handle_caa_request() below */
+{
+	char buf[64*1024];
+	int len;
+	/* Use possibly dynamic top domain in reply */
+	char *resp_domain = q->name + topdomain_offset;
+
+	len = dns_encode_caa_response(buf, sizeof(buf), q, resp_domain);
+	if (len < 1) {
+		warnx("dns_encode_caa_response doesn't fit");
+		return;
+	}
+
+	if (debug >= 2) {
+		fprintf(stderr, "TX: client %s, type %d, name %s, %d bytes NS reply\n",
+			format_addr(&q->from, q->fromlen), q->type, q->name, len);
+	}
+	if (sendto(dns_fd, buf, len, 0, (struct sockaddr*)&q->from, q->fromlen) <= 0) {
+		warn("ns reply send error");
+	}
+}
+
 static void
 handle_ns_request(int dns_fd, struct query *q, int topdomain_offset)
 /* Mostly identical to handle_a_request() below */
@@ -1689,12 +1713,13 @@ tunnel_dns(int tun_fd, int dns_fd, struct dnsfd *dns_fds, int bind_fd)
 	if ((read = read_dns(dns_fd, dns_fds, tun_fd, &q)) <= 0)
 		return 0;
 
+	domain_len = query_datalen(q.name, topdomain);
+
 	if (debug >= 2) {
-		fprintf(stderr, "RX: client %s, type %d, name %s\n",
+		fprintf(stderr, "RX: client %s, type %d, name %s, domain_len=%d\n",
-			format_addr(&q.from, q.fromlen), q.type, q.name);
+			format_addr(&q.from, q.fromlen), q.type, q.name, domain_len);
 	}
 
-	domain_len = query_datalen(q.name, topdomain);
 	if (domain_len >= 0) {
 		/* This is a query we can handle */
 
@@ -1740,10 +1765,19 @@ tunnel_dns(int tun_fd, int dns_fd, struct dnsfd *dns_fds, int bind_fd)
 		case T_NS:
 			handle_ns_request(dns_fd, &q, domain_len);
 			break;
+		case T_CAA:
+			handle_caa_request(dns_fd, &q, domain_len);
+			break;
 		default:
+			if (debug >= 0) {
+				fprintf(stderr, "WARN: can't handle request of type: %d\n", q.type);
+			}
 			break;
 		}
 	} else {
+		if (debug >= 0) {
+			fprintf(stderr, "WARN: can't handle non-authoritiative domain request");
+		}
 		/* Forward query to other port ? */
 		if (bind_fd) {
 			forward_query(bind_fd, &q);