nslookup: implement support for SRV records

Add support for querying and parsing SRV DNS records.

function                                             old     new   delta
send_queries                                        1711    1865    +154
qtypes                                                72      80      +8

Signed-off-by: Jo-Philipp Wich <jo@mein.io>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

networking/nslookup.c

@@ -283,6 +283,7 @@ static const struct {
 	{ ns_t_cname, "CNAME" },
 	{ ns_t_mx,    "MX"    },
 	{ ns_t_txt,   "TXT"   },
+	{ ns_t_srv,   "SRV"   },
 	{ ns_t_ptr,   "PTR"   },
 	{ ns_t_any,   "ANY"   },
 };
@@ -435,6 +436,25 @@ static int parse_reply(const unsigned char *msg, size_t len)
 			}
 			break;
 
+		case ns_t_srv:
+			if (rdlen < 6) {
+				//printf("SRV record too short\n");
+				return -1;
+			}
+
+			cp = ns_rr_rdata(rr);
+			n = ns_name_uncompress(ns_msg_base(handle), ns_msg_end(handle),
+			                       cp + 6, dname, sizeof(dname));
+
+			if (n < 0) {
+				//printf("Unable to uncompress domain: %s\n", strerror(errno));
+				return -1;
+			}
+
+			printf("%s\tservice = %u %u %u %s\n", ns_rr_name(rr),
+				ns_get16(cp), ns_get16(cp + 2), ns_get16(cp + 4), dname);
+			break;
+
 		case ns_t_soa:
 			if (rdlen < 20) {
 				dbg("SOA record too short:%d\n", rdlen);