Introduce FEATURE_PREFER_IPV4_ADDRESS. If selected, we have:

function                                             old     new   delta
str2sockaddr                                         328     344     +16

2 files changed, 31 insertions, 3 deletions

diff --git a/libbb/xconnect.c b/libbb/xconnect.c
index cb5ac2c8e..91c12f4d3 100644
--- a/libbb/xconnect.c
+++ b/libbb/xconnect.c
@@ -125,6 +125,7 @@ USE_FEATURE_IPV6(sa_family_t af,)
         int rc;
         len_and_sockaddr *r = NULL;
         struct addrinfo *result = NULL;
+        struct addrinfo *used_res;
         const char *org_host = host; /* only for error msg */
         const char *cp;
         struct addrinfo hint;
@@ -169,9 +170,21 @@ USE_FEATURE_IPV6(sa_family_t af,)
                         xfunc_die();
                 goto ret;
         }
-        r = xmalloc(offsetof(len_and_sockaddr, sa) + result->ai_addrlen);
-        r->len = result->ai_addrlen;
-        memcpy(&r->sa, result->ai_addr, result->ai_addrlen);
+        used_res = result;
+#if ENABLE_FEATURE_PREFER_IPV4_ADDRESS
+        while (1) {
+                if (used_res->ai_family == AF_INET)
+                        break;
+                used_res = used_res->ai_next;
+                if (!used_res) {
+                        used_res = result;
+                        break;
+                }
+        }
+#endif
+        r = xmalloc(offsetof(len_and_sockaddr, sa) + used_res->ai_addrlen);
+        r->len = used_res->ai_addrlen;
+        memcpy(&r->sa, used_res->ai_addr, used_res->ai_addrlen);
         set_nport(r, htons(port));
  ret:
         freeaddrinfo(result);
diff --git a/networking/Config.in b/networking/Config.in
index b5b4597c4..b50aacf9f 100644
--- a/networking/Config.in
+++ b/networking/Config.in
@@ -12,6 +12,21 @@ config FEATURE_IPV6
           Enable IPv6 support in busybox.
           This adds IPv6 support in the networking applets.
 
+config FEATURE_PREFER_IPV4_ADDRESS
+        bool "Preferentially use IPv4 addresses from DNS queries"
+        default y
+        depends on FEATURE_IPV6
+        help
+          Use IPv4 address of network host if it has one.
+
+          If this option is off, the first returned address will be used.
+          This may cause problems when your DNS server is IPv6-capable and
+          is returning IPv6 host addresses too. If IPv6 address
+          precedes IPv4 one in DNS reply, busybox network applets
+          (e.g. wget) will use IPv6 address. On an IPv6-incapable host
+          or network applets will fail to connect to the host
+          using IPv6 address.
+
 config VERBOSE_RESOLUTION_ERRORS
         bool "Verbose resolution errors"
         default n