turns out there is one more error message that can signal missing IPv6

support in the kernel

CHANGES

@@ -1,4 +1,5 @@
 0.23:
+  also recognize EPFNOSUPPORT as EAFNOSUPPORT (groan)
 
 0.22:
   uh, the scope_id detection #defined the wrong constant.  libowfat

socket/socket_tcp6.c

@@ -11,6 +11,9 @@
 #ifndef EAFNOSUPPORT
 #define EAFNOSUPPORT EINVAL
 #endif
+#ifndef EPFNOSUPPORT
+#define EPFNOSUPPORT EAFNOSUPPORT
+#endif
 
 int socket_tcp6(void)
 {
@@ -21,7 +24,7 @@ int socket_tcp6(void)
   if (noipv6) goto compat;
   s = winsock2errno(socket(PF_INET6,SOCK_STREAM,0));
   if (s == -1) {
-    if (errno == EINVAL || errno == EAFNOSUPPORT) {
+    if (errno == EINVAL || errno == EAFNOSUPPORT || errno == EPFNOSUPPORT) {
 compat:
       s=socket(AF_INET,SOCK_STREAM,0);
       noipv6=1;

socket/socket_udp6.c

@@ -11,6 +11,9 @@
 #ifndef EAFNOSUPPORT
 #define EAFNOSUPPORT EINVAL
 #endif
+#ifndef EPFNOSUPPORT
+#define EPFNOSUPPORT EAFNOSUPPORT
+#endif
 
 int socket_udp6(void)
 {
@@ -21,7 +24,7 @@ int socket_udp6(void)
   if (noipv6) goto compat;
   s = winsock2errno(socket(PF_INET6,SOCK_DGRAM,0));
   if (s == -1) {
-    if (errno == EINVAL || errno == EAFNOSUPPORT) {
+    if (errno == EINVAL || errno == EAFNOSUPPORT || errno == EPFNOSUPPORT) {
 compat:
       s=winsock2errno(socket(AF_INET,SOCK_DGRAM,0));
       noipv6=1;