diff options
| -rw-r--r-- | src/slirp.c | 135 |
1 files changed, 131 insertions, 4 deletions
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 @@ static const uint8_t special_ethaddr[ETH_ALEN] = { 0x52, 0x55, 0x00, 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 @@ int get_dns_addr(struct in_addr *pdns_addr) 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; } |