[Qemu-devel] [PATCH] sockets: Normalize test for addrinfo flag AI_V4MAPPED

[Antonio Huete Jiménez]

From 2b4d9d8cb617445af8f3b062f917dfea42dbdc27 Mon Sep 17 00:00:00 2001
From: Antonio Huete Jimenez <address@hidden>
Date: Thu, 2 Nov 2017 17:46:24 +0100
Subject: [PATCH] sockets: Normalize test for addrinfo flag AI_V4MAPPED

Signed-off-by: Antonio Huete Jimenez <address@hidden>
---
 util/qemu-sockets.c | 54  
+++++++++++++++++++++++++++++++++--------------------
 1 file changed, 34 insertions(+), 20 deletions(-)

diff --git a/util/qemu-sockets.c b/util/qemu-sockets.c
index b47fb45885..ce35b6a998 100644
--- a/util/qemu-sockets.c
+++ b/util/qemu-sockets.c
@@ -44,7 +44,6 @@
 # define AI_NUMERICSERV 0
 #endif

-
 static int inet_getport(struct addrinfo *e)
 {
     struct sockaddr_in *i4;
@@ -149,6 +148,31 @@ int inet_ai_family_from_address(InetSocketAddress *addr,
     return PF_UNSPEC;
 }

+static int
+check_ai_v4mapped(const char *host, const char *port, struct addrinfo *ai,
+               struct addrinfo *res)
+{
+    static int useV4Mapped = -1;
+    int rc;
+
+    /* At least FreeBSD and OS-X 10.6 declare AI_V4MAPPED but
+     * then don't implement it in their getaddrinfo().
+     * Unconditionally deselect AI_V4MAPPED option upon
+     * getaddrinfo() failure, the next call to it will have to
+     * do the error handling.
+     */
+    if (atomic_read(&useV4Mapped) == -1) {
+        rc = getaddrinfo(host, port, ai, &res);
+        if (rc == 0 && (ai->ai_flags & AI_V4MAPPED)) {
+            atomic_set(&useV4Mapped, 1);
+        } else {
+            atomic_set(&useV4Mapped, 0);
+        }
+    }
+
+    return useV4Mapped;
+}
+
 static int create_fast_reuse_socket(struct addrinfo *e)
 {
     int slisten = qemu_socket(e->ai_family, e->ai_socktype, e->ai_protocol);
@@ -378,14 +402,10 @@ 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_ADDRCONFIG;
-    if (atomic_read(&useV4Mapped)) {
-        ai.ai_flags |= AI_V4MAPPED;
-    }
+    ai.ai_flags = AI_CANONNAME | AI_ADDRCONFIG | AI_V4MAPPED;
     ai.ai_family = inet_ai_family_from_address(saddr, &err);
     ai.ai_socktype = SOCK_STREAM;

@@ -399,21 +419,11 @@ static struct addrinfo  
*inet_parse_connect_saddr(InetSocketAddress *saddr,
         return NULL;
     }

-    /* 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);
+    if ((check_ai_v4mapped(saddr->host, saddr->port, &ai, res)) == 0) {
         ai.ai_flags &= ~AI_V4MAPPED;
-        rc = getaddrinfo(saddr->host, saddr->port, &ai, &res);
     }
-    if (rc != 0) {
+
+    if ((rc = getaddrinfo(saddr->host, saddr->port, &ai, &res)) != 0) {
         error_setg(errp, "address resolution failed for %s:%s: %s",
                    saddr->host, saddr->port, gai_strerror(rc));
         return NULL;
@@ -469,7 +479,7 @@ static int inet_dgram_saddr(InetSocketAddress *sraddr,

     /* lookup peer addr */
     memset(&ai,0, sizeof(ai));
-    ai.ai_flags = AI_CANONNAME | AI_V4MAPPED | AI_ADDRCONFIG;
+    ai.ai_flags = AI_CANONNAME | AI_ADDRCONFIG | AI_V4MAPPED;
     ai.ai_family = inet_ai_family_from_address(sraddr, &err);
     ai.ai_socktype = SOCK_DGRAM;

@@ -488,6 +498,10 @@ static int inet_dgram_saddr(InetSocketAddress *sraddr,
         goto err;
     }

+    if ((check_ai_v4mapped(addr, port, &ai, &peer)) == 0) {
+        ai.ai_flags &= ~AI_V4MAPPED;
+    }
+
     if ((rc = getaddrinfo(addr, port, &ai, &peer)) != 0) {
         error_setg(errp, "address resolution failed for %s:%s: %s",  
addr, port,
                    gai_strerror(rc));
--
2.14.1