Add initial support for hostname lookup via resolver

2 files changed, 132 insertions, 0 deletions

diff --git a/gresolv/gresolv.c b/gresolv/gresolv.c
index d1aa8d27..8256b0b7 100644
--- a/gresolv/gresolv.c
+++ b/gresolv/gresolv.c
@@ -25,6 +25,7 @@
 
 #include <errno.h>
 #include <unistd.h>
+#include <stdarg.h>
 #include <string.h>
 #include <resolv.h>
 #include <sys/socket.h>
@@ -34,11 +35,14 @@
 #include "gresolv.h"
 
 struct resolv_nameserver {
+	GResolv *resolv;
+
 	char *address;
 	uint16_t port;
 	unsigned long flags;
 
 	GIOChannel *udp_channel;
+	guint udp_watch;
 };
 
 struct _GResolv {
@@ -51,11 +55,30 @@ struct _GResolv {
 	gpointer debug_data;
 };
 
+static inline void debug(GResolv *resolv, const char *format, ...)
+{
+	char str[256];
+	va_list ap;
+
+	if (resolv->debug_func == NULL)
+		return;
+
+	va_start(ap, format);
+
+	if (vsnprintf(str, sizeof(str), format, ap) > 0)
+		resolv->debug_func(str, resolv->debug_data);
+
+	va_end(ap);
+}
+
 static void free_nameserver(struct resolv_nameserver *nameserver)
 {
 	if (nameserver == NULL)
 		return;
 
+	if (nameserver->udp_watch > 0)
+		g_source_remove(nameserver->udp_watch);
+
 	if (nameserver->udp_channel != NULL)
 		g_io_channel_unref(nameserver->udp_channel);
 
@@ -75,6 +98,89 @@ static void flush_nameservers(GResolv *resolv)
 	resolv->nameserver_list = NULL;
 }
 
+static int send_query(GResolv *resolv, const unsigned char *buf, int len)
+{
+	GList *list;
+
+	if (resolv->nameserver_list == NULL)
+		return -ENOENT;
+
+	for (list = g_list_first(resolv->nameserver_list);
+					list; list = g_list_next(list)) {
+		struct resolv_nameserver *nameserver = list->data;
+		int sk, sent;
+
+		if (nameserver->udp_channel == NULL)
+			continue;
+
+		sk = g_io_channel_unix_get_fd(nameserver->udp_channel);
+
+		sent = send(sk, buf, len, 0);
+	}
+
+	return 0;
+}
+
+static void parse_response(struct resolv_nameserver *nameserver,
+					const unsigned char *buf, int len)
+{
+	GResolv *resolv = nameserver->resolv;
+	ns_msg msg;
+	ns_rr rr;
+	int i, rcode;
+
+	debug(resolv, "response from %s", nameserver->address);
+
+	ns_initparse(buf, len, &msg);
+
+	rcode = ns_msg_getflag(msg, ns_f_rcode);
+
+	debug(resolv, "msg id: 0x%04x rcode: %d count: %d",
+			ns_msg_id(msg), rcode, ns_msg_count(msg, ns_s_an));
+
+	for (i = 0; i < ns_msg_count(msg, ns_s_an); i++) {
+		char result[100];
+
+		ns_parserr(&msg, ns_s_an, i, &rr);
+
+		if (ns_rr_class(rr) != ns_c_in)
+			continue;
+
+		if (ns_rr_type(rr) != ns_t_a)
+			continue;
+
+		if (ns_rr_rdlen(rr) != NS_INADDRSZ)
+			continue;
+
+		inet_ntop(AF_INET, ns_rr_rdata(rr), result, sizeof(result));
+
+		debug(resolv, "result: %s", result);
+	}
+}
+
+static gboolean received_udp_data(GIOChannel *channel, GIOCondition cond,
+							gpointer user_data)
+{
+	struct resolv_nameserver *nameserver = user_data;
+	unsigned char buf[4096];
+	int sk, len;
+
+	if (cond & (G_IO_NVAL | G_IO_ERR | G_IO_HUP)) {
+		nameserver->udp_watch = 0;
+		return FALSE;
+	}
+
+	sk = g_io_channel_unix_get_fd(nameserver->udp_channel);
+
+	len = recv(sk, buf, sizeof(buf), 0);
+	if (len < 12)
+		return TRUE;
+
+	parse_response(nameserver, buf, len);
+
+	return TRUE;
+}
+
 static int connect_udp_channel(struct resolv_nameserver *nameserver)
 {
 	struct sockaddr_in sin;
@@ -102,6 +208,10 @@ static int connect_udp_channel(struct resolv_nameserver *nameserver)
 
 	g_io_channel_set_close_on_unref(nameserver->udp_channel, TRUE);
 
+	nameserver->udp_watch = g_io_add_watch(nameserver->udp_channel,
+						G_IO_IN, received_udp_data,
+								nameserver);
+
 	return 0;
 }
 
@@ -178,9 +288,13 @@ int g_resolv_add_nameserver(GResolv *resolv, const char *address,
 		return -EIO;
 	}
 
+	nameserver->resolv = resolv;
+
 	resolv->nameserver_list = g_list_append(resolv->nameserver_list,
 								nameserver);
 
+	debug(resolv, "setting nameserver %s", address);
+
 	return 0;
 }
 
@@ -191,3 +305,19 @@ void g_resolv_flush_nameservers(GResolv *resolv)
 
 	flush_nameservers(resolv);
 }
+
+int g_resolv_lookup_hostname(GResolv *resolv, const char *hostname)
+{
+	unsigned char buf[4096];
+	int len;
+
+	debug(resolv, "lookup hostname %s", hostname);
+
+	len = res_mkquery(ns_o_query, hostname, ns_c_in, ns_t_a,
+					NULL, 0, NULL, buf, sizeof(buf));
+
+	if (send_query(resolv, buf, len) < 0)
+		return -EIO;
+
+	return 0;
+}
diff --git a/gresolv/gresolv.h b/gresolv/gresolv.h
index 40b49728..baafd355 100644
--- a/gresolv/gresolv.h
+++ b/gresolv/gresolv.h
@@ -48,6 +48,8 @@ int g_resolv_add_nameserver(GResolv *resolv, const char *address,
 					uint16_t port, unsigned long flags);
 void g_resolv_flush_nameservers(GResolv *resolv);
 
+int g_resolv_lookup_hostname(GResolv *resolv, const char *hostname);
+
 #ifdef __cplusplus
 }
 #endif