diff --git a/Makefile b/Makefile
index 00fbb72..389a8f0 100644
--- a/Makefile
+++ b/Makefile
@@ -2,12 +2,12 @@ all: t byte.a fmt.a scan.a str.a uint.a open.a stralloc.a unix.a socket.a buffer
 
 VPATH=str:byte:fmt:scan:uint:open:stralloc:unix:socket:buffer:mmap
 
+# comment out the following line if you don't want to build with the
+# diet libc (http://www.fefe.de/dietlibc/).
+DIET=diet -Os
 CC=gcc
 CFLAGS=-I. -pipe -Wall -O2 -pipe -fomit-frame-pointer
-#CFLAGS=-I. -pipe -Wall -Os -march=pentiumpro -fomit-frame-pointer -fschedule-insns2 -Wall
-#CFLAGS=-I. -I../dietlibc/include -pipe -Wall -Os -malign-functions=2 -fschedule-insns2 -g
-#CFLAGS=-I../dietlibc/include -I. -pipe -Wall -Os -march=pentiumpro -mcpu=athlon -fomit-frame-pointer -fschedule-insns2 -Wall
-#CFLAGS=-I../dietlibc/include -pipe -Os -march=pentiumpro -mcpu=pentiumpro -fomit-frame-pointer -fschedule-insns2 -Wall
+#CFLAGS=-pipe -Os -march=pentiumpro -mcpu=pentiumpro -fomit-frame-pointer -fschedule-insns2 -Wall
 
 BYTE_OBJS=$(patsubst byte/%.c,%.o,$(wildcard byte/*.c))
 FMT_OBJS=$(patsubst fmt/%.c,%.o,$(wildcard fmt/*.c))
@@ -49,14 +49,40 @@ $(BUFFER_OBJS) $(MMAP_OBJS)
 
 %.a:
 	ar cr $@ $^
+	-ranlib $@
 
 t: t.o socket.a stralloc.a buffer.a scan.a uint.a mmap.a open.a fmt.a \
 str.a byte.a
-	$(DIET)$(CC) -g -o $@ $^
+	$(DIET) $(CC) -g -o $@ $^
 
 .PHONY: clean tar
 clean:
-	rm -f *.o *.a core t
+	rm -f *.o *.a core t haveip6.h haven2i.h
+
+VERSION=libowfat-$(shell head -1 CHANGES|sed 's/://')
+CURNAME=$(notdir $(shell pwd))
+
+tar: clean rename
+	cd ..; tar cvvf $(VERSION).tar.bz2 $(VERSION) --use=bzip2 --exclude CVS
+
+rename:
+	if test $(CURNAME) != $(VERSION); then cd .. && mv $(CURNAME) $(VERSION); fi
+
+haveip6.h:
+	-rm -f $@
+	if $(DIET) $(CC) -c tryip6.c >/dev/null 2>&1; then echo "#define LIBC_HAS_IP6"; fi > $@
+
+haven2i.h:
+	-rm -f $@
+	if $(DIET) $(CC) -o t tryn2i.c >/dev/null 2>&1; then echo "#define HAVE_N2I"; fi > $@
+
+havesl.h:
+	-rm -f $@
+	if $(DIET) $(CC) -o t trysl.c >/dev/null 2>&1; then echo "#define HAVE_SOCKLEN_T"; fi > $@
+
+socket_accept6.o socket_connect6.o socket_local6.o socket_mchopcount6.o \
+socket_mcjoin6.o socket_mcleave6.o socket_mcloop6.o socket_recv6.o \
+socket_remote6.o socket_send6.o socket_tcp6.o socket_udp6.o: haveip6.h
+
+socket_getifidx.o socket_getifname.o: haven2i.h
 
-tar:
-	cd .. && tar cf libowfat.tar.bz2 libowfat --use=bzip2 --exclude CVS
diff --git a/haveip6.h b/haveip6.h
deleted file mode 100644
index 87b5bd2..0000000
--- a/haveip6.h
+++ /dev/null
@@ -1,2 +0,0 @@
-
-#define LIBC_HAS_IP6
diff --git a/haven2i.h b/haven2i.h
deleted file mode 100644
index fd50644..0000000
--- a/haven2i.h
+++ /dev/null
@@ -1 +0,0 @@
-#define HAVE_N2I
diff --git a/socket/socket_tcp6.c b/socket/socket_tcp6.c
index 3fc7825..845cb5e 100644
--- a/socket/socket_tcp6.c
+++ b/socket/socket_tcp6.c
@@ -1,9 +1,33 @@
 #include <sys/types.h>
 #include <sys/socket.h>
 #include <netinet/in.h>
-
+#include <errno.h>
+#include "haveip6.h"
 #include "socket.h"
 
-int socket_tcp6(void) {
-  return socket(PF_INET6,SOCK_STREAM,IPPROTO_TCP);
+#ifndef EAFNOSUPPORT
+#define EAFNOSUPPORT EINVAL
+#endif
+
+int socket_tcp6(void)
+{
+#ifdef LIBC_HAS_IP6
+  int s;
+
+  if (noipv6) goto compat;
+  s = socket(PF_INET6,SOCK_STREAM,0);
+  if (s == -1) {
+    if (errno == EINVAL || errno == EAFNOSUPPORT) {
+compat:
+      s=socket(AF_INET,SOCK_STREAM,0);
+      noipv6=1;
+      if (s==-1) return -1;
+    } else
+    return -1;
+  }
+  return s;
+#else
+  return socket_tcp();
+#endif
 }
+
diff --git a/socket/socket_udp6.c b/socket/socket_udp6.c
index 82de50f..6c27d15 100644
--- a/socket/socket_udp6.c
+++ b/socket/socket_udp6.c
@@ -1,9 +1,32 @@
 #include <sys/types.h>
 #include <sys/socket.h>
 #include <netinet/in.h>
-
+#include <errno.h>
+#include "haveip6.h"
 #include "socket.h"
 
-int socket_udp6(void) {
-  return socket(PF_INET6,SOCK_DGRAM,IPPROTO_UDP);
+#ifndef EAFNOSUPPORT
+#define EAFNOSUPPORT EINVAL
+#endif
+
+int socket_udp6(void)
+{
+#ifdef LIBC_HAS_IP6
+  int s;
+
+  if (noipv6) goto compat;
+  s = socket(PF_INET6,SOCK_DGRAM,0);
+  if (s == -1) {
+    if (errno == EINVAL || errno == EAFNOSUPPORT) {
+compat:
+      s=socket(AF_INET,SOCK_DGRAM,0);
+      noipv6=1;
+      if (s==-1) return -1;
+    } else
+    return -1;
+  }
+  return s;
+#else
+  return socket_udp();
+#endif
 }
diff --git a/t.c b/t.c
index b44fa53..a37bfb7 100644
--- a/t.c
+++ b/t.c
@@ -14,12 +14,11 @@
      __asm__ __volatile__ ("rdtsc" : "=a" (low) : : "edx")
 
 int main(int argc,char* argv[]) {
-  char buf[100];
-  buf[fmt_ulong(buf,0)]=0;
-  puts(buf);
-#if 0
-  buffer_putspace(buffer_1);
-  buffer_flush(buffer_1);
+#if 1
+  buffer_putulong(buffer_1,23);
+//  buffer_putspace(buffer_1);
+  buffer_putsflush(buffer_1,"\n");
+//  buffer_flush(buffer_1);
 #endif
 #if 0
   long a,b,c;
diff --git a/tryip6.c b/tryip6.c
new file mode 100644
index 0000000..e0d7cfb
--- /dev/null
+++ b/tryip6.c
@@ -0,0 +1,8 @@
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <netinet/in.h>
+
+main() {
+  struct sockaddr_in6 sa;
+  sa.sin6_family = PF_INET6;
+}
diff --git a/tryn2i.c b/tryn2i.c
new file mode 100644
index 0000000..84c3a08
--- /dev/null
+++ b/tryn2i.c
@@ -0,0 +1,8 @@
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <net/if.h>
+
+int main() {
+  static char ifname[IFNAMSIZ];
+  char *tmp=if_indextoname(0,ifname);
+}
diff --git a/trysl.c b/trysl.c
new file mode 100644
index 0000000..5a5b355
--- /dev/null
+++ b/trysl.c
@@ -0,0 +1,7 @@
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <netinet/in.h>
+
+main() {
+  socklen_t t;
+}