experimental offset

git-svn-id: https://map66.svn.sourceforge.net/svnroot/map66@23 3484d885-4da6-438d-b19d-107d078dd756

3 files changed, 38 insertions, 8 deletions

diff --git a/README.dbk b/README.dbk
index 4c58cb5..a0f122b 100644
--- a/README.dbk
+++ b/README.dbk
@@ -304,11 +304,12 @@ ip6tables -t mangle -A FORWARD -p tcp --tcp-flags SYN,RST SYN -j TCPMSS --clamp-
 
       <para>If you already deployed ULA adresses in your network, you may be
       interested in a solution that runs on my Freifunk router. The router
-      uses the IPv4 192.168.65.65/26 on it's LAN interface. The OLSR-based
-      mesh network uses an fdca:ffee:babe::/64 prefix. The following internal
-      mapping is configured for this: </para>
+      uses the IPv4 192.168.65.65/26 on it's LAN interface. WIthin the
+      OLSR-based mesh network, any interface uses an fdca:ffee:babe::/64
+      prefix. The following internal mapping is configured for this: </para>
 
-      <programlisting></programlisting>
+      <programlisting>ip6tables -t mangle -I PREROUTING -i br0 -s 2002:c0a8:4141::/64 -j MAP66 --src-to fdca:ffee:babe::/64
+ip6tables -t mangle -I POSTROUTING -o br0 -d fdca:ffee:babe::/64 -j MAP66 --dst-to 2002:c0a8:4141::/64</programlisting>
     </section>
   </section>
 
diff --git a/ip6t_MAP66.h b/ip6t_MAP66.h
index 291956d..c3e124f 100644
--- a/ip6t_MAP66.h
+++ b/ip6t_MAP66.h
@@ -12,7 +12,8 @@
 
 #define IP6T_MAP66_OPT_DST_TO 0x01
 #define IP6T_MAP66_OPT_SRC_TO 0x02
-#define IP6T_MAP66_OPT_NOCHECK 0x04
+#define IP6T_MAP66_OPT_OFFSET 0x04
+#define IP6T_MAP66_OPT_NOCHECK 0x08
 
 struct ip6t_MAP66_info {
 	struct in6_addr	pfix_dst_to;	/* The prefix to map destination addrs to */
@@ -21,6 +22,7 @@ struct ip6t_MAP66_info {
 	struct in6_addr	pfix_src_to;	/* The prefix to map source addrs from */
 	u_int16_t	pfix_src_len;	/* Source addrs prefix length DIV 16 */
 	u_int16_t	pfix_src_csum;	/* Pre-calculated csum for source addrs */
+	u_int16_t	mapoffset;	/* Offset in addrs for balanced csum change */
 	u_int16_t	mapflags;	/* Some flags */
 };
 
diff --git a/libip6t_MAP66.c b/libip6t_MAP66.c
index a5502c3..9fab6a6 100644
--- a/libip6t_MAP66.c
+++ b/libip6t_MAP66.c
@@ -61,6 +61,7 @@ static void MAP66_help(void)
 "MAP66 target options\n"
 "  --" IP6T_MAP66_DST_TO " ipv6addr/prefixlength (Prefix to map IPv6 destination address to)\n"
 "  --" IP6T_MAP66_SRC_TO " ipv6addr/prefixlength (Prefix to map IPv6 source address to)\n"
+"  --offset number                (Use another part of addrs to balance csum)\n"
 "  --nocheck                      (Disables the do-not-map-to-my-addr check)\n"
 "\n"
 "Note: you need two ip6tables rules to map an internal network\n"
@@ -140,14 +141,36 @@ static int MAP66_parse(
 				xtables_error(PARAMETER_PROBLEM, "Invalid IPv6 address in --" IP6T_MAP66_SRC_TO ": \"%s\"", optarg);
 			}
 			i = atoi(p + 1);
-			if (0 >= i || 128 <= i || 0 != i % 16) {
-				xtables_error(PARAMETER_PROBLEM, "Invalid prefix length in --" IP6T_MAP66_SRC_TO ": \"%s\" (use /112, /96 .. /16)", p + 1);
+			if (0 > i || 128 <= i || 0 != i % 16) {
+				xtables_error(PARAMETER_PROBLEM, "Invalid prefix length in --" IP6T_MAP66_SRC_TO ": \"%s\" (use /112, /96 .. /0)", p + 1);
 			}
 			info->pfix_src_len = i / 16;
 			info->pfix_src_csum = ~csum16((const u_int16_t *)&info->pfix_src_to, info->pfix_src_len);
 			return 1;
 		break;
 		case '3':
+			if (!optarg) {
+				xtables_error(PARAMETER_PROBLEM, "--offset: You must specify a value");
+			}
+			if (xtables_check_inverse(optarg, &invert, NULL, 0
+#if IPTABLES_VERSION_CODE >= IPTABLES_VERSION_CMP(1,4,6)
+				,argv
+#endif
+			)) {
+				xtables_error(PARAMETER_PROBLEM, "Unexpected `!' after --offset");
+			}
+			if (0 != (IP6T_MAP66_OPT_OFFSET & *flags)) {
+				xtables_error(PARAMETER_PROBLEM, "Multiple --offset not supported");
+			}
+			*flags |= IP6T_MAP66_OPT_OFFSET;
+			i = atoi(p + 1);
+			if (0 > i || 14 <= i) {
+				xtables_error(PARAMETER_PROBLEM, "Invalid value in --offset: \"%s\" (use 0-14)", p + 1);
+			}
+			info->mapoffset = i;
+			return 0;
+		break;
+		case '4':
 			if (0 != (IP6T_MAP66_OPT_NOCHECK & *flags)) {
 				xtables_error(PARAMETER_PROBLEM, "Multiple --nocheck not supported");
 			}
@@ -178,6 +201,9 @@ static void MAP66_save(
 	if (0 != (IP6T_MAP66_OPT_SRC_TO & info->mapflags)) {
 		printf("--" IP6T_MAP66_SRC_TO " %s/%d ", inet_ntop(AF_INET6, &info->pfix_src_to, s, sizeof(s)), 16 * info->pfix_src_len);
 	}
+	if (0 != info->mapoffset)) {
+		printf("--offset %d ", info->mapoffset);
+	}
 	if (0 != (IP6T_MAP66_OPT_NOCHECK & info->mapflags)) {
 		printf("--nocheck ");
 	}
@@ -186,7 +212,8 @@ static void MAP66_save(
 static struct option MAP66_opts[] = {
 	{ .name = IP6T_MAP66_DST_TO, .has_arg = 1, .flag = NULL, .val = '1' },
 	{ .name = IP6T_MAP66_SRC_TO, .has_arg = 1, .flag = NULL, .val = '2' },
-	{ .name = "nocheck", .has_arg = 0, .flag = NULL, .val = '3' },
+	{ .name = "offset", .has_arg = 1, .flag = NULL, .val = '3' },
+	{ .name = "nocheck", .has_arg = 0, .flag = NULL, .val = '4' },
 	{ .name = NULL }
 };