Fix remaining localhost resolution issues.

net/base/host_resolver_proc.cc

Index: net/base/host_resolver_proc.cc
diff --git a/net/base/host_resolver_proc.cc b/net/base/host_resolver_proc.cc
index fd350dffa998baa4c0c21197e2f7667c311c0cf2..86304dcec2e65d34356d463b983e2ee17dc7d95e 100644
--- a/net/base/host_resolver_proc.cc
+++ b/net/base/host_resolver_proc.cc
@@ -18,6 +18,42 @@
 
 namespace net {
 
+namespace {
+
+bool IsAllLocalhostOfOneFamily(const struct addrinfo* ai) {
+  bool saw_v4_localhost = false;
+  bool saw_v6_localhost = false;
+  for (; ai != NULL; ai = ai->ai_next) {
+    switch (ai->ai_family) {
+      case AF_INET: {
+        const struct sockaddr_in* addr_in =
+            reinterpret_cast<struct sockaddr_in*>(ai->ai_addr);
+        if ((ntohl(addr_in->sin_addr.s_addr) & 0xff000000) == 0x7f000000)
+          saw_v4_localhost = true;
+        else
+          return false;
+        break;
+      }
+      case AF_INET6: {
+        const struct sockaddr_in6* addr_in6 =
+            reinterpret_cast<struct sockaddr_in6*>(ai->ai_addr);
+        if (IN6_IS_ADDR_LOOPBACK(&addr_in6->sin6_addr))
+          saw_v6_localhost = true;
+        else
+          return false;
+        break;
+      }
+      default:
+        NOTREACHED();
+        return false;
+    }
+  }
+
+  return saw_v4_localhost != saw_v6_localhost;
+}
+
+}  // namespace
+
 HostResolverProc* HostResolverProc::default_proc_ = NULL;
 
 HostResolverProc::HostResolverProc(HostResolverProc* previous) {
@@ -161,15 +197,36 @@ int SystemHostResolverProc(const std::string& host,
   hints.ai_socktype = SOCK_STREAM;
 
   int err = getaddrinfo(host.c_str(), NULL, &hints, &ai);
+  bool should_retry = false;
 #if defined(OS_POSIX) && !defined(OS_MACOSX) && !defined(OS_OPENBSD)
   // If we fail, re-initialise the resolver just in case there have been any
   // changes to /etc/resolv.conf and retry. See http://crbug.com/11380 for info.
   if (err && DnsReloadTimerHasExpired()) {
     res_nclose(&_res);
     if (!res_ninit(&_res))
-      err = getaddrinfo(host.c_str(), NULL, &hints, &ai);
+      should_retry = true;
   }
 #endif
+  // If the lookup was restricted (either by address family, or address
+  // detection), and the results where all localhost of a single family,
+  // maybe we should retry.  There were several bugs related to these
+  // issues, for example http://crbug.com/42058 and http://crbug.com/49024
+  if ((hints.ai_family != AF_UNSPEC || hints.ai_flags & AI_ADDRCONFIG) &&
+      err == 0 && IsAllLocalhostOfOneFamily(ai)) {

[willchan no longer on Chromium, 2010/09/03 19:36:50]

I personally think "err == OK" is more readable, but I defer to you.

[vandebo (ex-Chrome), 2010/09/03 19:42:18]

err is the result of getaddrinfo, not a chrome network function.  While OK is 0,
it could be something else.  I think == 0 is the right thing, though maybe a bit
pedantic.

[willchan no longer on Chromium, 2010/09/03 20:23:07]

Oops, sorry, I thought this was a net::Error.  I completely agree.

+    if (host_resolver_flags & HOST_RESOLVER_DEFAULT_FAMILY_SET_DUE_TO_NO_IPV6) {
+      hints.ai_family = AF_UNSPEC;
+      should_retry = true;
+    }
+    if (hints.ai_flags & AI_ADDRCONFIG) {
+      hints.ai_flags &= ~AI_ADDRCONFIG;
+      should_retry = true;
+    }
+  }
+  if (should_retry) {
+    freeaddrinfo(ai);

[willchan no longer on Chromium, 2010/09/03 19:36:50]

don't you need a NULL check here?  In the line 207 condition, won't ai be NULL? 
delete does a NULL check, but I don't think free() does (I'm not sure).

[vandebo (ex-Chrome), 2010/09/03 19:42:18]

From man 3 free: 'If ptr is NULL, no operation is performed.'

[willchan no longer on Chromium, 2010/09/03 20:23:07]

Clearly I haven't done C programming in forever.

+    ai = NULL;
+    err = getaddrinfo(host.c_str(), NULL, &hints, &ai);
+  }
 
   if (err) {
     if (os_error) {