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Merge "Only look up A records if the system has IPv4." into gingerbread

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2 parents 2e23e29 + ba96e30 commit 2081fda69a68505c914324797400b1b798516904 David Turner committed with Android (Google) Code Review
Showing with 59 additions and 29 deletions.
  1. +59 −29 libc/netbsd/net/getaddrinfo.c
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88 libc/netbsd/net/getaddrinfo.c
@@ -340,35 +340,55 @@ str2number(const char *p)
return -1;
}
-/* Determine whether IPv6 connectivity is available. */
+/*
+ * Connect a UDP socket to a given unicast address. This will cause no network
+ * traffic, but will fail fast if the system has no or limited reachability to
+ * the destination (e.g., no IPv4 address, no IPv6 default route, ...).
+ */
static int
-_have_ipv6() {
- /*
- * Connect a UDP socket to an global unicast IPv6 address. This will
- * cause no network traffic, but will fail fast if the system has no or
- * limited IPv6 connectivity (e.g., only a link-local address).
- */
- static const struct sockaddr_in6 sin6_test = {
- /* family, port, flow label */
- AF_INET6, 0, 0,
- /* 2000:: */
- {{{ 0x20, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 }}},
- /* scope ID */
- 0};
- sockaddr_union addr_test;
- addr_test.in6 = sin6_test;
- int s = socket(PF_INET6, SOCK_DGRAM, IPPROTO_UDP);
+_test_connect(int pf, struct sockaddr *addr, size_t addrlen) {
+ int s = socket(pf, SOCK_DGRAM, IPPROTO_UDP);
if (s < 0)
return 0;
int ret;
do {
- ret = connect(s, &addr_test.generic, sizeof(addr_test.in6));
+ ret = connect(s, addr, addrlen);
} while (ret < 0 && errno == EINTR);
- int have_ipv6 = (ret == 0);
+ int success = (ret == 0);
do {
ret = close(s);
} while (ret < 0 && errno == EINTR);
- return have_ipv6;
+ return success;
+}
+
+/*
+ * The following functions determine whether IPv4 or IPv6 connectivity is
+ * available in order to implement AI_ADDRCONFIG.
+ *
+ * Strictly speaking, AI_ADDRCONFIG should not look at whether connectivity is
+ * available, but whether addresses of the specified family are "configured
+ * on the local system". However, bionic doesn't currently support getifaddrs,
+ * so checking for connectivity is the next best thing.
+ */
+static int
+_have_ipv6() {
+ static const struct sockaddr_in6 sin6_test = {
+ .sin6_family = AF_INET6,
+ .sin6_addr.s6_addr = { // 2000::
+ 0x20, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}
+ };
+ sockaddr_union addr = { .in6 = sin6_test };
+ return _test_connect(PF_INET6, &addr.generic, sizeof(addr.in6));
+}
+
+static int
+_have_ipv4() {
+ static const struct sockaddr_in sin_test = {
+ .sin_family = AF_INET,
+ .sin_addr.s_addr = __constant_htonl(0x08080808L) // 8.8.8.8
+ };
+ sockaddr_union addr = { .in = sin_test };
+ return _test_connect(PF_INET, &addr.generic, sizeof(addr.in));
}
int
@@ -1687,17 +1707,27 @@ _dns_getaddrinfo(void *rv, void *cb_data, va_list ap)
q.qclass = C_IN;
q.answer = buf->buf;
q.anslen = sizeof(buf->buf);
- /* If AI_ADDRCONFIG, lookup IPv6 only if we have connectivity */
- if (!(pai->ai_flags & AI_ADDRCONFIG) || _have_ipv6()) {
+ int query_ipv6 = 1, query_ipv4 = 1;
+ if (pai->ai_flags & AI_ADDRCONFIG) {
+ query_ipv6 = _have_ipv6();
+ query_ipv4 = _have_ipv4();
+ }
+ if (query_ipv6) {
q.qtype = T_AAAA;
- q.next = &q2;
- q2.name = name;
- q2.qclass = C_IN;
- q2.qtype = T_A;
- q2.answer = buf2->buf;
- q2.anslen = sizeof(buf2->buf);
- } else {
+ if (query_ipv4) {
+ q.next = &q2;
+ q2.name = name;
+ q2.qclass = C_IN;
+ q2.qtype = T_A;
+ q2.answer = buf2->buf;
+ q2.anslen = sizeof(buf2->buf);
+ }
+ } else if (query_ipv4) {
q.qtype = T_A;
+ } else {
+ free(buf);
+ free(buf2);
+ return NS_NOTFOUND;
}
break;
case AF_INET:

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