nc: make connecting to IPv4 from IPv6-enabled hosts easier

(was requiring -s <local addr>)

1 files changed, 20 insertions, 12 deletions

diff --git a/libbb/xconnect.c b/libbb/xconnect.c
index e7d510678..b90aa9add 100644
--- a/libbb/xconnect.c
+++ b/libbb/xconnect.c
@@ -208,23 +208,31 @@ len_and_sockaddr* xdotted2sockaddr(const char *host, int port)
         return str2sockaddr(host, port, AF_UNSPEC, AI_NUMERICHOST | DIE_ON_ERROR);
 }
 
-int xsocket_type(len_and_sockaddr **lsap, int sock_type)
+int xsocket_type(len_and_sockaddr **lsap, USE_FEATURE_IPV6(int family,) int sock_type)
 {
+        SKIP_FEATURE_IPV6(enum { family = AF_INET };)
         len_and_sockaddr *lsa;
         int fd;
-        int len = sizeof(struct sockaddr_in);
-        int family = AF_INET;
+        int len;
 
 #if ENABLE_FEATURE_IPV6
-        fd = socket(AF_INET6, sock_type, 0);
-        if (fd >= 0) {
-                len = sizeof(struct sockaddr_in6);
-                family = AF_INET6;
-        } else
+        if (family == AF_UNSPEC) {
+                fd = socket(AF_INET6, sock_type, 0);
+                if (fd >= 0) {
+                        family = AF_INET6;
+                        goto done;
+                }
+                family = AF_INET;
+        }
 #endif
-        {
-                fd = xsocket(AF_INET, sock_type, 0);
+        fd = xsocket(family, sock_type, 0);
+        len = sizeof(struct sockaddr_in);
+#if ENABLE_FEATURE_IPV6
+        if (family == AF_INET6) {
+ done:
+                len = sizeof(struct sockaddr_in6);
         }
+#endif
         lsa = xzalloc(offsetof(len_and_sockaddr, sa) + len);
         lsa->len = len;
         lsa->sa.sa_family = family;
@@ -234,7 +242,7 @@ int xsocket_type(len_and_sockaddr **lsap, int sock_type)
 
 int xsocket_stream(len_and_sockaddr **lsap)
 {
-        return xsocket_type(lsap, SOCK_STREAM);
+        return xsocket_type(lsap, USE_FEATURE_IPV6(AF_UNSPEC,) SOCK_STREAM);
 }
 
 static int create_and_bind_or_die(const char *bindaddr, int port, int sock_type)
@@ -247,7 +255,7 @@ static int create_and_bind_or_die(const char *bindaddr, int port, int sock_type)
                 /* user specified bind addr dictates family */
                 fd = xsocket(lsa->sa.sa_family, sock_type, 0);
         } else {
-                fd = xsocket_type(&lsa, sock_type);
+                fd = xsocket_type(&lsa, USE_FEATURE_IPV6(AF_UNSPEC,) sock_type);
                 set_nport(lsa, htons(port));
         }
         setsockopt_reuseaddr(fd);