Fixes suggested by @Florob in #147.

doc/tcp.html

@@ -65,6 +65,12 @@ href=#bind><tt>connect</tt></a>, depending on the address
 family obtained from the resolver.
 </p>
 
+<p class=note>
+Note: Before the choice between IPv4 and IPv6 happens,
+the internal socket object is invalid and therefore <a
+href=#setoption><tt>setoption</tt></a> will fail.
+</p>
+
 <!-- socket.tcp +++++++++++++++++++++++++++++++++++++++++++++++++++++++++ -->
 
 <p class=name id="socket.tcp4">

doc/udp.html

@@ -76,6 +76,12 @@ href=#setsockname><tt>sockname</tt></a>, depending on the address
 family obtained from the resolver.
 </p>
 
+<p class=note>
+Note: Before the choice between IPv4 and IPv6 happens,
+the internal socket object is invalid and therefore <a
+href=#setoption><tt>setoption</tt></a> will fail.
+</p>
+
 <!-- socket.udp4 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++ -->
 
 <p class="name" id="socket.udp">

src/inet.c

@@ -352,8 +352,13 @@ static void inet_pushresolved(lua_State *L, struct hostent *hp)
 /*-------------------------------------------------------------------------*\
 * Tries to create a new inet socket
 \*-------------------------------------------------------------------------*/
-const char *inet_trycreate(p_socket ps, int family, int type) {
+const char *inet_trycreate(p_socket ps, int family, int type, int protocol) {
-    return socket_strerror(socket_create(ps, family, type, 0));
+    const char *err = socket_strerror(socket_create(ps, family, type, protocol));
+    if (err == NULL && family == AF_INET6) {
+        int yes = 1;
+        setsockopt(*ps, IPPROTO_IPV6, IPV6_V6ONLY, (void *)&yes, sizeof(yes));
+    }
+    return err;
 }
 
 /*-------------------------------------------------------------------------*\
@@ -408,8 +413,8 @@ const char *inet_tryconnect(p_socket ps, int *family, const char *address,
          * not enter this branch. */
         if (current_family != iterator->ai_family || *ps == SOCKET_INVALID) {
             socket_destroy(ps);
-            err = socket_strerror(socket_create(ps, iterator->ai_family,
+            err = inet_trycreate(ps, iterator->ai_family,
-                iterator->ai_socktype, iterator->ai_protocol));
+                iterator->ai_socktype, iterator->ai_protocol);
             if (err) continue;
             current_family = iterator->ai_family;
             /* set non-blocking before connect */
@@ -466,8 +471,8 @@ const char *inet_trybind(p_socket ps, int *family, const char *address,
     for (iterator = resolved; iterator; iterator = iterator->ai_next) {
         if (current_family != iterator->ai_family || *ps == SOCKET_INVALID) {
             socket_destroy(ps);
-            err = socket_strerror(socket_create(ps, iterator->ai_family,
+            err = inet_trycreate(ps, iterator->ai_family,
-                        iterator->ai_socktype, iterator->ai_protocol));
+                        iterator->ai_socktype, iterator->ai_protocol);
             if (err) continue;
             current_family = iterator->ai_family;
         }

src/inet.h

@@ -24,7 +24,7 @@
 
 int inet_open(lua_State *L);
 
-const char *inet_trycreate(p_socket ps, int family, int type);
+const char *inet_trycreate(p_socket ps, int family, int type, int protocol);
 const char *inet_tryconnect(p_socket ps, int *family, const char *address,
         const char *serv, p_timeout tm, struct addrinfo *connecthints);
 const char *inet_trybind(p_socket ps, int *family, const char *address,

src/tcp.c

@@ -355,39 +355,29 @@ static int meth_settimeout(lua_State *L)
 * Creates a master tcp object
 \*-------------------------------------------------------------------------*/
 static int tcp_create(lua_State *L, int family) {
-    t_socket sock;
-    /* if family is AF_UNSPEC, we create an AF_INET socket
-     * but store AF_UNSPEC into tcp-family. This will allow it
-     * later be replaced with an AF_INET6 socket if
-     * trybind or tryconnect prefer it instead. */
-    const char *err = inet_trycreate(&sock, family == AF_UNSPEC?
-        AF_INET: family, SOCK_STREAM);
-    /* try to allocate a system socket */
-    if (!err) {
-        /* allocate tcp object */
     p_tcp tcp = (p_tcp) lua_newuserdata(L, sizeof(t_tcp));
     memset(tcp, 0, sizeof(t_tcp));
     /* set its type as master object */
     auxiliar_setclass(L, "tcp{master}", -1);
-        /* initialize remaining structure fields */
+    /* if family is AF_UNSPEC, we leave the socket invalid and
-        socket_setnonblocking(&sock);
+     * store AF_UNSPEC into family. This will allow it to later be
-        if (family == AF_INET6) {
+     * replaced with an AF_INET6 or AF_INET socket upon first use. */
-            int yes = 1;
+    tcp->sock = SOCKET_INVALID;
-            setsockopt(sock, IPPROTO_IPV6, IPV6_V6ONLY,
+    tcp->family = family;
-                (void *)&yes, sizeof(yes));
-        }
-        tcp->sock = sock;
     io_init(&tcp->io, (p_send) socket_send, (p_recv) socket_recv,
             (p_error) socket_ioerror, &tcp->sock);
     timeout_init(&tcp->tm, -1, -1);
     buffer_init(&tcp->buf, &tcp->io, &tcp->tm);
-        tcp->family = family;
+    if (family != AF_UNSPEC) {
-        return 1;
+        const char *err = inet_trycreate(&tcp->sock, family, SOCK_STREAM, 0);
-    } else {
+        if (err != NULL) {
             lua_pushnil(L);
             lua_pushstring(L, err);
             return 2;
         }
+        socket_setnonblocking(&tcp->sock);
+    }
+    return 1;
 }
 
 static int global_create(lua_State *L) {

src/udp.c

@@ -365,7 +365,6 @@ static int meth_setpeername(lua_State *L) {
         inet_trydisconnect(&udp->sock, udp->family, tm);
         auxiliar_setclass(L, "udp{unconnected}", 1);
     }
-    /* change class to connected or unconnected depending on address */
     lua_pushnumber(L, 1);
     return 1;
 }
@@ -410,34 +409,25 @@ static int meth_setsockname(lua_State *L) {
 * Creates a master udp object
 \*-------------------------------------------------------------------------*/
 static int udp_create(lua_State *L, int family) {
-    t_socket sock;
-    /* if family is AF_UNSPEC, we create an AF_INET socket
-     * but store AF_UNSPEC into tcp-family. This will allow it
-     * later be replaced with an AF_INET6 socket if
-     * trybind or tryconnect prefer it instead. */
-    const char *err = inet_trycreate(&sock, family == AF_UNSPEC?
-        AF_INET: family, SOCK_DGRAM);
-    /* try to allocate a system socket */
-    if (!err) {
     /* allocate udp object */
     p_udp udp = (p_udp) lua_newuserdata(L, sizeof(t_udp));
     auxiliar_setclass(L, "udp{unconnected}", -1);
-        /* initialize remaining structure fields */
+    /* if family is AF_UNSPEC, we leave the socket invalid and
-        socket_setnonblocking(&sock);
+     * store AF_UNSPEC into family. This will allow it to later be
-        if (family == AF_INET6) {
+     * replaced with an AF_INET6 or AF_INET socket upon first use. */
-            int yes = 1;
+    udp->sock = SOCKET_INVALID;
-            setsockopt(sock, IPPROTO_IPV6, IPV6_V6ONLY,
-                (void *)&yes, sizeof(yes));
-        }
-        udp->sock = sock;
     timeout_init(&udp->tm, -1, -1);
     udp->family = family;
-        return 1;
+    if (family != AF_UNSPEC) {
-    } else {
+        const char *err = inet_trycreate(&udp->sock, family, SOCK_DGRAM, 0);
+        if (err != NULL) {
             lua_pushnil(L);
             lua_pushstring(L, err);
             return 2;
         }
+        socket_setnonblocking(&udp->sock);
+    }
+    return 1;
 }
 
 static int global_create(lua_State *L) {

test/testclnt.lua

@@ -304,15 +304,20 @@ function isclosed(c)
 end
 
 function active_close()
-    reconnect()
+    local tcp = socket.tcp4()
-    if isclosed(data) then fail("should not be closed") end
+    if isclosed(tcp) then fail("should not be closed") end
-    data:close()
+    tcp:close()
-    if not isclosed(data) then fail("should be closed") end
+    if not isclosed(tcp) then fail("should be closed") end
-    data = nil
+    tcp = socket.tcp()
-    local udp = socket.udp()
+    if not isclosed(tcp) then fail("should be closed") end
+    tcp = nil
+    local udp = socket.udp4()
     if isclosed(udp) then fail("should not be closed") end
     udp:close()
     if not isclosed(udp) then fail("should be closed") end
+    udp = socket.udp()
+    if not isclosed(udp) then fail("should be closed") end
+    udp = nil
     pass("ok")
 end
 
@@ -368,7 +373,7 @@ function test_selectbugs()
     pass("invalid input: ok")
     local toomany = {}
     for i = 1, socket._SETSIZE+1 do
-        toomany[#toomany+1] = socket.udp()
+        toomany[#toomany+1] = socket.udp4()
     end
     if #toomany > socket._SETSIZE then
         local e = pcall(socket.select, toomany, nil, 0.1)