ipv6-gen-slaac: Utility to generate SLAAC address

Given an IPv6 network & MAC address generate the corresponding SLAAC
address. e.g

    $ ./ipv6-gen-slaac 2001:db8:a:b:: 00:24:1d:ba:80:00
    SLAAC : 2001:db8:a:b:224:1dff:feba:8000

Signed-off-by: Andrew Clayton <andrew@digital-domain.net>

Author: ac000

.gitignore

@@ -4,6 +4,7 @@ gen-ula
 ipv6-arpa
 ipv6-extract-mac
 ipv6-fmt
+ipv6-gen-slaac
 ipv6-isin
 ipv6-range
 mac-to-eui64

Makefile

@@ -18,7 +18,7 @@ ifneq "$(GLIBC_VER_OK)" "1"
 endif
 
 all: ipv6-range ipv6-arpa ipv6-isin gen-ula mac-to-eui64 mac-type \
-	ipv6-extract-mac prefix-to-mask mask-to-prefix ipv6-fmt
+	ipv6-extract-mac prefix-to-mask mask-to-prefix ipv6-fmt ipv6-gen-slaac
 
 ipv6-range: ipv6-range.c
 	$(CC) $(CFLAGS) -o $@ $<
@@ -50,6 +50,9 @@ mask-to-prefix: mask-to-prefix.c
 ipv6-fmt: ipv6-fmt.c
 	$(CC) $(CFLAGS) -o $@ $<
 
+ipv6-gen-slaac: ipv6-gen-slaac.c
+	$(CC) $(CFLAGS) -o $@ $<
+
 clean:
 	rm -f ipv6-range ipv6-arpa ipv6-isin gen-ula mac-to-eui64 mac-type \
-	ipv6-extract-mac prefix-to-mask mask-to-prefix ipv6-fmt
+	ipv6-extract-mac prefix-to-mask mask-to-prefix ipv6-fmt ipv6-gen-slaac

README

@@ -98,5 +98,11 @@ ipv6-fmt		- Given an IPv6 address format it in compressed,
     Expanded    : 2001:0db8:0000:0000:0000:dead:0000:beef
     URI Literal : [2001:db8::dead:0:beef]
 
+ipv6-gen-slaac		- Given an IPv6 network & MAC address, generate the
+			  corresponding SLAAC address.
+
+    $ ./ipv6-gen-slaac 2001:db8:a:b:: 00:24:1d:ba:80:00
+    SLAAC : 2001:db8:a:b:224:1dff:feba:8000
+
 These tools are licensed under the GNU General Public License Version 2 or
 the GNU Lesser General Public License Version 2.1

ipv6-gen-slaac.c

@@ -0,0 +1,61 @@
+/*
+ * ipv6-gen-slaac.c	- Given an IPv6 network & MAC address create the
+ *			  corresponding SLAAC address.
+ *
+ * Copyright (C) 2017	Andrew Clayton <andrew@digital-domain.net>
+ *
+ * Licensed under the GNU General Public License Version 2 or
+ * the GNU Lesser General Public License Version 2.1
+ *
+ * See GPLv2 & LGPLv2.1 in the source tree.
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <arpa/inet.h>
+
+#include "short_types.h"
+
+int main(int argc, char *argv[])
+{
+	int i;
+	int len;
+	u8 mac[8];
+	u8 slaacn[sizeof(struct in6_addr)];
+	char slaac[INET6_ADDRSTRLEN];
+
+	if (argc < 2) {
+		fprintf(stderr, "Usage: ipv6-gen-slaac <IPv6 network> <MAC address>\n");
+		exit(EXIT_FAILURE);
+	}
+
+	len = snprintf(slaac, sizeof(slaac), "%s", argv[1]);
+	if (slaac[len-1] == ':' && slaac[len-2] == ':')
+		slaac[len-1] = '\0';
+	else if (slaac[len-1] != ':')
+		snprintf(slaac + len, sizeof(slaac), ":");
+
+	mac[0] = strtoul(argv[2], NULL, 16);
+	mac[1] = strtoul(argv[2]+3, NULL, 16);
+	mac[2] = strtoul(argv[2]+6, NULL, 16);
+	mac[3] = 0xff;
+	mac[4] = 0xfe;
+	mac[5] = strtoul(argv[2]+9, NULL, 16);
+	mac[6] = strtoul(argv[2]+12, NULL, 16);
+	mac[7] = strtoul(argv[2]+15, NULL, 16);
+
+	/* Toggle the (U/L) bit 0000 00*0 */
+	mac[0] ^= 1 << 1;
+
+	for (i = 0; i < 8; i += 2)
+		snprintf(slaac + strlen(slaac), sizeof(slaac), "%02x%02x%s",
+				mac[i], mac[i+1], i+1 < 7 ? ":" : "");
+
+	/* Display in compressed form */
+	inet_pton(AF_INET6, slaac, slaacn);
+	inet_ntop(AF_INET6, slaacn, slaac, INET6_ADDRSTRLEN);
+	printf("SLAAC : %s\n", slaac);
+
+	exit(EXIT_SUCCESS);
+}