Merge branch 'dns6' into 'master'
IPv6 DNS proxying support
Closes #55
See merge request slirp/libslirp!110
diff --git a/src/slirp.c b/src/slirp.c
index ef098de..5e08b53 100644
--- a/src/slirp.c
+++ b/src/slirp.c
@@ -34,6 +34,37 @@
#undef if_mtu
#endif
+#if defined(_WIN32)
+
+#define INITIAL_DNS_ADDR_BUF_SIZE 32 * 1024
+#define REALLOC_RETRIES 5
+
+// Broadcast site local DNS resolvers. We do not use these because they are
+// highly unlikely to be valid.
+// https://www.ietf.org/proceedings/52/I-D/draft-ietf-ipngwg-dns-discovery-03.txt
+static const struct in6_addr SITE_LOCAL_DNS_BROADCAST_ADDRS[] = {
+ {
+ {{
+ 0xfe, 0xc0, 0x00, 0x00, 0x00, 0x00, 0xff, 0xff,
+ 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01
+ }}
+ },
+ {
+ {{
+ 0xfe, 0xc0, 0x00, 0x00, 0x00, 0x00, 0xff, 0xff,
+ 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x02
+ }}
+ },
+ {
+ {{
+ 0xfe, 0xc0, 0x00, 0x00, 0x00, 0x00, 0xff, 0xff,
+ 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x03,
+ }}
+ },
+};
+
+#endif
+
int slirp_debug;
/* Define to 1 if you want KEEPALIVE timers */
@@ -51,14 +82,10 @@
unsigned curtime;
static struct in_addr dns_addr;
-#ifndef _WIN32
static struct in6_addr dns6_addr;
static uint32_t dns6_scope_id;
-#endif
static unsigned dns_addr_time;
-#ifndef _WIN32
static unsigned dns6_addr_time;
-#endif
#define TIMEOUT_FAST 2 /* milliseconds */
#define TIMEOUT_SLOW 499 /* milliseconds */
@@ -112,8 +139,108 @@
return 0;
}
+int is_site_local_dns_broadcast(struct in6_addr *address)
+{
+ int i;
+ for (i = 0; i < G_N_ELEMENTS(SITE_LOCAL_DNS_BROADCAST_ADDRS); i++) {
+ if (in6_equal(address, &SITE_LOCAL_DNS_BROADCAST_ADDRS[i])) {
+ return 1;
+ }
+ }
+ return 0;
+}
+
+void print_dns_v6_address(struct in6_addr address)
+{
+ char address_str[INET6_ADDRSTRLEN] = "";
+ if (inet_ntop(AF_INET6, &address, address_str, INET6_ADDRSTRLEN)
+ == NULL) {
+ DEBUG_ERROR("Failed to stringify IPv6 address for logging.");
+ return;
+ }
+ DEBUG_CALL("IPv6 DNS server found: %s", address_str);
+}
+
+// Gets the first valid DNS resolver with an IPv6 address.
+// Ignores any site local broadcast DNS servers, as these
+// are on deprecated addresses and not generally expected
+// to work. Further details at:
+// https://www.ietf.org/proceedings/52/I-D/draft-ietf-ipngwg-dns-discovery-03.txt
+int get_ipv6_dns_server(struct in6_addr *dns_server_address, uint32_t *scope_id)
+{
+ PIP_ADAPTER_ADDRESSES addresses = NULL;
+ PIP_ADAPTER_ADDRESSES address = NULL;
+ IP_ADAPTER_DNS_SERVER_ADDRESS *dns_server = NULL;
+ struct sockaddr_in6 *dns_v6_addr = NULL;
+
+ ULONG buf_size = INITIAL_DNS_ADDR_BUF_SIZE;
+ DWORD res = ERROR_BUFFER_OVERFLOW;
+ int i;
+
+ for (i = 0; i < REALLOC_RETRIES; i++) {
+ // If non null, we hit buffer overflow, free it so we can try again.
+ if (addresses != NULL) {
+ g_free(addresses);
+ }
+
+ addresses = g_malloc(buf_size);
+ res = GetAdaptersAddresses(AF_UNSPEC, GAA_FLAG_INCLUDE_PREFIX, NULL,
+ addresses, &buf_size);
+
+ if (res != ERROR_BUFFER_OVERFLOW) {
+ break;
+ }
+ }
+
+ if (res != NO_ERROR) {
+ DEBUG_ERROR("Failed to get IPv6 DNS addresses due to error %lX", res);
+ goto failure;
+ }
+
+ address = addresses;
+ for (address = addresses; address != NULL; address = address->Next) {
+ for (dns_server = address->FirstDnsServerAddress;
+ dns_server != NULL;
+ dns_server = dns_server->Next) {
+
+ if (dns_server->Address.lpSockaddr->sa_family != AF_INET6) {
+ continue;
+ }
+
+ dns_v6_addr = (struct sockaddr_in6 *)dns_server->Address.lpSockaddr;
+ if (is_site_local_dns_broadcast(&dns_v6_addr->sin6_addr) == 0) {
+ print_dns_v6_address(dns_v6_addr->sin6_addr);
+ *dns_server_address = dns_v6_addr->sin6_addr;
+ *scope_id = dns_v6_addr->sin6_scope_id;
+
+ g_free(addresses);
+ return 0;
+ }
+ }
+ }
+
+ DEBUG_ERROR("No IPv6 DNS servers found.\n");
+
+failure:
+ g_free(addresses);
+ return -1;
+}
+
int get_dns6_addr(struct in6_addr *pdns6_addr, uint32_t *scope_id)
{
+ if (!in6_zero(&dns6_addr) && (curtime - dns6_addr_time) < TIMEOUT_DEFAULT) {
+ *pdns6_addr = dns6_addr;
+ *scope_id = dns6_scope_id;
+ return 0;
+ }
+
+ if (get_ipv6_dns_server(pdns6_addr, scope_id) == 0) {
+ dns6_addr = *pdns6_addr;
+ dns6_addr_time = curtime;
+ dns6_scope_id = *scope_id;
+ return 0;
+ }
+
return -1;
}
