add libip

src/libip/ipaux.c

diff --git a/src/libip/ipaux.c b/src/libip/ipaux.c
new file mode 100644
index 0000000..215b37e
--- /dev/null
+++ b/src/libip/ipaux.c
@@ -0,0 +1,102 @@
+#include <u.h>
+#include <libc.h>
+#include <ip.h>
+
+/*
+ *  well known IP addresses
+ */
+uchar IPv4bcast[IPaddrlen] = {
+	0, 0, 0, 0,
+	0, 0, 0, 0,
+	0, 0, 0xff, 0xff,
+	0xff, 0xff, 0xff, 0xff
+};
+uchar IPv4allsys[IPaddrlen] = {
+	0, 0, 0, 0,
+	0, 0, 0, 0,
+	0, 0, 0xff, 0xff,
+	0xe0, 0, 0, 0x01
+};
+uchar IPv4allrouter[IPaddrlen] = {
+	0, 0, 0, 0,
+	0, 0, 0, 0,
+	0, 0, 0xff, 0xff,
+	0xe0, 0, 0, 0x02
+};
+uchar IPallbits[IPaddrlen] = {
+	0xff, 0xff, 0xff, 0xff,
+	0xff, 0xff, 0xff, 0xff,
+	0xff, 0xff, 0xff, 0xff,
+	0xff, 0xff, 0xff, 0xff
+};
+uchar IPnoaddr[IPaddrlen];
+
+/*
+ *  prefix of all v4 addresses
+ */
+uchar v4prefix[IPaddrlen] = {
+	0, 0, 0, 0,
+	0, 0, 0, 0,
+	0, 0, 0xff, 0xff,
+	0, 0, 0, 0
+};
+
+int
+isv4(uchar *ip)
+{
+	return memcmp(ip, v4prefix, IPv4off) == 0;
+}
+
+/*
+ *  the following routines are unrolled with no memset's to speed
+ *  up the usual case
+ */
+void
+v4tov6(uchar *v6, uchar *v4)
+{
+	v6[0] = 0;
+	v6[1] = 0;
+	v6[2] = 0;
+	v6[3] = 0;
+	v6[4] = 0;
+	v6[5] = 0;
+	v6[6] = 0;
+	v6[7] = 0;
+	v6[8] = 0;
+	v6[9] = 0;
+	v6[10] = 0xff;
+	v6[11] = 0xff;
+	v6[12] = v4[0];
+	v6[13] = v4[1];
+	v6[14] = v4[2];
+	v6[15] = v4[3];
+}
+
+int
+v6tov4(uchar *v4, uchar *v6)
+{
+	if(v6[0] == 0
+	&& v6[1] == 0
+	&& v6[2] == 0
+	&& v6[3] == 0
+	&& v6[4] == 0
+	&& v6[5] == 0
+	&& v6[6] == 0
+	&& v6[7] == 0
+	&& v6[8] == 0
+	&& v6[9] == 0
+	&& v6[10] == 0xff
+	&& v6[11] == 0xff)
+	{
+		v4[0] = v6[12];
+		v4[1] = v6[13];
+		v4[2] = v6[14];
+		v4[3] = v6[15];
+		return 0;
+	} else {
+		memset(v4, 0, 4);
+		if(memcmp(v6, IPnoaddr, IPaddrlen) == 0)
+			return 0;
+		return -1;
+	}
+}