[Qemu-devel] [PATCH v2] util: retry getaddrinfo if getting EAI_BADFLAGS with AI_V4MAPPED

["Daniel P. Berrange" <berrange@redhat.com>]

The FreeBSD header files define the AI_V4MAPPED but its
implementation of getaddrinfo() always returns an error
when that flag is set. eg

  address resolution failed for localhost:9000: Invalid value for ai_flags

There are also reports of the same problem on OS-X 10.6

Since AI_V4MAPPED is not critical functionality, if we
get an EAI_BADFLAGS error then just retry without the
AI_V4MAPPED flag set. Use a static var to cache this
status so we don't have to retry on every single call.

Also remove its use from the test suite since it serves
no useful purpose there.

Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
---

Changed in v2:

 - Fix test case usage of AI_V4MAPPED
 - Don't disable AI_V4MAPPED at build time, detect it
   at runtime, so we catch any platform with broken impl

 tests/test-io-channel-socket.c |  5 +----
 util/qemu-sockets.c            | 19 ++++++++++++++++++-
 2 files changed, 19 insertions(+), 5 deletions(-)

diff --git a/tests/test-io-channel-socket.c b/tests/test-io-channel-socket.c
index 9d94adb..855306b 100644
--- a/tests/test-io-channel-socket.c
+++ b/tests/test-io-channel-socket.c
@@ -27,9 +27,6 @@
 #ifndef AI_ADDRCONFIG
 # define AI_ADDRCONFIG 0
 #endif
-#ifndef AI_V4MAPPED
-# define AI_V4MAPPED 0
-#endif
 #ifndef EAI_ADDRFAMILY
 # define EAI_ADDRFAMILY 0
 #endif
@@ -42,7 +39,7 @@ static int check_bind(const char *hostname, bool *has_proto)
     int ret = -1;
 
     memset(&ai, 0, sizeof(ai));
-    ai.ai_flags = AI_CANONNAME | AI_V4MAPPED | AI_ADDRCONFIG;
+    ai.ai_flags = AI_CANONNAME | AI_ADDRCONFIG;
     ai.ai_family = AF_UNSPEC;
     ai.ai_socktype = SOCK_STREAM;
 
diff --git a/util/qemu-sockets.c b/util/qemu-sockets.c
index b87e17f..0d53691 100644
--- a/util/qemu-sockets.c
+++ b/util/qemu-sockets.c
@@ -29,6 +29,7 @@
 #ifndef AI_ADDRCONFIG
 # define AI_ADDRCONFIG 0
 #endif
+
 #ifndef AI_V4MAPPED
 # define AI_V4MAPPED 0
 #endif
@@ -354,10 +355,14 @@ static struct addrinfo *inet_parse_connect_saddr(InetSocketAddress *saddr,
     struct addrinfo ai, *res;
     int rc;
     Error *err = NULL;
+    static int useV4Mapped = 1;
 
     memset(&ai, 0, sizeof(ai));
 
-    ai.ai_flags = AI_CANONNAME | AI_V4MAPPED | AI_ADDRCONFIG;
+    ai.ai_flags = AI_CANONNAME | AI_ADDRCONFIG;
+    if (atomic_read(&useV4Mapped)) {
+        ai.ai_flags |= AI_V4MAPPED;
+    }
     ai.ai_family = inet_ai_family_from_address(saddr, &err);
     ai.ai_socktype = SOCK_STREAM;
 
@@ -373,6 +378,18 @@ static struct addrinfo *inet_parse_connect_saddr(InetSocketAddress *saddr,
 
     /* lookup */
     rc = getaddrinfo(saddr->host, saddr->port, &ai, &res);
+
+    /* At least FreeBSD and OS-X 10.6 declare AI_V4MAPPED but
+     * then don't implement it in their getaddrinfo(). Detect
+     * this and retry without the flag since that's preferrable
+     * to a fatal error
+     */
+    if (rc == EAI_BADFLAGS &&
+        (ai.ai_flags & AI_V4MAPPED)) {
+        atomic_set(&useV4Mapped, 0);
+        ai.ai_flags &= ~AI_V4MAPPED;
+        rc = getaddrinfo(saddr->host, saddr->port, &ai, &res);
+    }
     if (rc != 0) {
         error_setg(errp, "address resolution failed for %s:%s: %s",
                    saddr->host, saddr->port, gai_strerror(rc));
-- 
2.5.5