Add new package for configuring 6rd tunnels.

This patch adds support for manually configuring 6rd tunnels. It depends on
the netifd patches I sent earlier, which add 6rd support.

A basic interface configuration looks like:

    config interface 'wan6'
      option proto '6rd'
      option peeraddr '192.0.2.1'
      option ip6prefix '2123::'
      option ip6prefixlen '16'
      option ip4prefixlen '0'

Where ip4prefixlen is optional and actually defaults to 0, which would use all
bits of the IPv4 in the calculated IPv6 subnet.

I believe it should be possible to configure a regular 6to4 tunnel using this,
and that we may want to merge the two eventually, but there are some larger

differences between the two at the moment:

 - 6rd addresses can be more difficult to calculate. My ISP, for example, has
   a setup with a v6 mask of 43 bits, and a v4 mask of 19.

 - 6to4 has support for configuring radvd. This is something we want, of
   course, but it seems best to deal with this in a separate patch.

Just creating a new package looked like the quickest way to get this in.

This work is based on the 6in4 package, and work by Stijn Tintel.

Signed-off-by: Stéphan Kochen <stephan@kochen.nl>

SVN-Revision: 32431

package/6rd/Makefile

@@ -0,0 +1,55 @@
+#
+# Copyright (C) 2010-2012 OpenWrt.org
+#
+# This is free software, licensed under the GNU General Public License v2.
+# See /LICENSE for more information.
+#
+
+include $(TOPDIR)/rules.mk
+
+PKG_NAME:=6rd
+PKG_VERSION:=1
+PKG_RELEASE:=1
+
+include $(INCLUDE_DIR)/package.mk
+
+define Package/6rd
+  SECTION:=ipv6
+  CATEGORY:=IPv6
+  DEPENDS:=+kmod-ipv6 +kmod-sit
+  TITLE:=6rd configuration support
+  MAINTAINER:=Stéphan Kochen <stephan@kochen.nl>
+  PKGARCH:=all
+endef
+
+define Package/6rd/description
+Provides support for 6rd tunnels in /etc/config/network.
+Refer to http://wiki.openwrt.org/doc/uci/network for
+configuration details.
+endef
+
+define Build/Prepare
+	mkdir -p $(PKG_BUILD_DIR)
+	$(CP) ./src/* $(PKG_BUILD_DIR)/
+endef
+
+define Build/Configure
+endef
+
+define Build/Compile
+	$(MAKE) -C $(PKG_BUILD_DIR) \
+		CC="$(TARGET_CC)" \
+		CFLAGS="$(TARGET_CFLAGS) -Wall" \
+		LDFLAGS="$(TARGET_LDFLAGS)"
+endef
+
+define Package/6rd/install
+	$(INSTALL_DIR) $(1)/usr/sbin
+	$(INSTALL_BIN) $(PKG_BUILD_DIR)/6rdcalc $(1)/usr/sbin/
+	$(INSTALL_DIR) $(1)/lib/netifd/proto
+	$(INSTALL_BIN) ./files/6rd.sh $(1)/lib/netifd/proto/6rd.sh
+	$(INSTALL_DIR) $(1)/etc/hotplug.d/iface
+	$(INSTALL_DATA) ./files/6rd.hotplug $(1)/etc/hotplug.d/iface/92-6rd
+endef
+
+$(eval $(call BuildPackage,6rd))

package/6rd/files/6rd.hotplug

@@ -0,0 +1,29 @@
+#!/bin/sh
+
+if [ "$ACTION" = ifup ]; then
+	. /lib/functions.sh
+
+	INCLUDE_ONLY=1
+	. /lib/netifd/proto/6rd.sh
+
+	include /lib/network
+	scan_interfaces
+
+	update_tunnel() {
+		local cfg="$1"
+
+		local proto
+		config_get proto "$cfg" proto
+		[ "$proto" = 6rd ] || return 0
+
+		local wandev
+		config_get wandev "$cfg" wan_device "$(find_6rd_wanif)"
+		[ "$wandev" = "$DEVICE" ] || return 0
+
+		local wanip=$(find_6rd_wanip "$wandev")
+
+		[ -n "$wanip" ] && ifup "$cfg"
+	}
+
+	config_foreach update_tunnel interface
+fi

package/6rd/files/6rd.sh

@@ -0,0 +1,83 @@
+#!/bin/sh
+# 6rd.sh - IPv6-in-IPv4 tunnel backend
+# Copyright (c) 2010-2012 OpenWrt.org
+
+[ -n "$INCLUDE_ONLY" ] || {
+	. /lib/functions.sh
+	. /lib/functions/network.sh
+	. ../netifd-proto.sh
+	init_proto "$@"
+}
+
+tun_error() {
+	local cfg="$1"; shift;
+
+	[ -n "$1" ] && proto_notify_error "$cfg" "$@"
+	proto_block_restart "$cfg"
+}
+
+proto_6rd_setup() {
+	local cfg="$1"
+	local iface="$2"
+	local link="6rd-$cfg"
+
+	local mtu ttl ipaddr peeraddr ip6prefix ip6prefixlen ip4prefixlen
+	json_get_vars mtu ttl ipaddr peeraddr ip6prefix ip6prefixlen ip4prefixlen
+
+	[ -z "$ip6prefix" -o -z "$peeraddr" ] && {
+		tun_error "$cfg" "MISSING_ADDRESS"
+		return
+	}
+
+	[ -z "$ipaddr" ] && {
+		local wanif
+		if ! network_find_wan wanif || ! network_get_ipaddr ipaddr "$wanif"; then
+			tun_error "$cfg" "NO_WAN_LINK"
+			return
+		fi
+	}
+
+	# Determine the relay prefix.
+	local ip4prefixlen="${ip4prefixlen:-0}"
+	local ip4prefix=$(ipcalc.sh "$ipaddr/$ip4prefixlen" | grep NETWORK)
+	ip4prefix="${ip4prefix#NETWORK=}"
+
+	# Determine our IPv6 address.
+	local ip6subnet=$(6rdcalc "$ip6prefix/$ip6prefixlen" "$ipaddr/$ip4prefixlen")
+	local ip6addr="${ip6subnet%%::*}::1"
+
+	proto_init_update "$link" 1
+	proto_add_ipv6_address "$ip6addr" "$ip6prefixlen"
+	proto_add_ipv6_route "::" 0 "::$peeraddr"
+
+	proto_add_tunnel
+	json_add_string mode sit
+	json_add_int mtu "${mtu:-1280}"
+	json_add_int ttl "${ttl:-64}"
+	json_add_string local "$ipaddr"
+	json_add_string 6rd-prefix "$ip6prefix/$ip6prefixlen"
+	json_add_string 6rd-relay-prefix "$ip4prefix/$ip4prefixlen"
+	proto_close_tunnel
+
+	proto_send_update "$cfg"
+}
+
+proto_6rd_teardown() {
+	local cfg="$1"
+}
+
+proto_6rd_init_config() {
+	no_device=1
+	available=1
+
+	proto_config_add_int "mtu"
+	proto_config_add_int "ttl"
+	proto_config_add_string "peeraddr"
+	proto_config_add_string "ip6prefix"
+	proto_config_add_string "ip6prefixlen"
+	proto_config_add_string "ip4prefixlen"
+}
+
+[ -n "$INCLUDE_ONLY" ] || {
+	add_protocol 6rd
+}

package/6rd/src/6rdcalc.c

@@ -0,0 +1,126 @@
+/*
+ * Utility used to calculate the 6rd subnet.
+ *
+ * Copyright 2012, Stéphan Kochen <stephan@kochen.nl>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/errno.h>
+#include <arpa/inet.h>
+#include <netinet/in.h>
+
+#define INET_PREFIXSTRLEN (INET_ADDRSTRLEN+3)
+#define INET6_PREFIXSTRLEN (INET6_ADDRSTRLEN+4)
+
+static void print_usage()
+{
+	fprintf(stderr, "Usage: 6rdcalc <v6 prefix>/<mask> <v4 address>/<mask>\n");
+	exit(1);
+}
+
+static void print_error()
+{
+	fprintf(stderr, "%s", strerror(errno));
+	exit(1);
+}
+
+static void parse_str(int af, char *str, void *addr, unsigned long *mask)
+{
+	int ret;
+	char *slash;
+
+	/* Split the address at the slash. */
+	if ((slash = strchr(str, '/')) == NULL)
+		print_usage();
+	*slash = '\0';
+
+	/* Parse the address. */
+	if ((ret = inet_pton(af, str, addr)) != 1) {
+		if (ret == 0)
+			print_usage();
+		else
+			print_error();
+	}
+
+	/* Parse the mask. */
+	*mask = strtoul(slash+1, NULL, 10);
+	if ((af == AF_INET  && *mask >  32) ||
+		(af == AF_INET6 && *mask > 128))
+		print_usage();
+}
+
+int main(int argc, const char **argv)
+{
+	char v6str[INET6_PREFIXSTRLEN], v4str[INET_PREFIXSTRLEN];
+	struct in6_addr v6;
+	struct in_addr v4;
+	unsigned long v6it, v4it, mask;
+	unsigned char *byte4, *byte6;
+	unsigned char bit4, bit6;
+
+	/* Check parameters. */
+	if (argc != 3)
+		print_usage();
+
+	/* Parse the v6 address. */
+	strncpy(v6str, argv[1], INET6_PREFIXSTRLEN);
+	v6str[INET6_PREFIXSTRLEN-1] = '\0';
+	parse_str(AF_INET6, v6str, &v6, &v6it);
+
+	/* Parse the v4 address */
+	strncpy(v4str, argv[2], INET_PREFIXSTRLEN);
+	v6str[INET_PREFIXSTRLEN-1] = '\0';
+	parse_str(AF_INET, v4str, &v4, &v4it);
+
+	/* Check if the combined mask is within bounds. */
+	mask = (32 - v4it) + v6it;
+	if (mask > 128)
+		print_usage();
+
+	/* Combine the addresses. */
+	while (v4it < 32) {
+		byte6 = (unsigned char *)(&v6.s6_addr) + (v6it >> 3);
+		byte4 = (unsigned char *)(&v4.s_addr)  + (v4it >> 3);
+		bit6 = 128 >> (v6it & 0x07);
+		bit4 = 128 >> (v4it & 0x07);
+
+		if (*byte4 & bit4)
+			*byte6 |= bit6;
+		else
+			*byte6 &= ~bit6;
+
+		v4it++; v6it++;
+	}
+
+	/* Clear remaining bits. */
+	while (v6it < 128) {
+		byte6 = (unsigned char *)(&v6.s6_addr) + (v6it >> 2);
+		bit6 = 128 >> (v6it & 0x07);
+
+		*byte6 &= ~bit6;
+
+		v6it++;
+	}
+
+	/* Print the subnet prefix. */
+	if (inet_ntop(AF_INET6, &v6, v6str, sizeof(v6str)) == NULL)
+		print_error();
+	printf("%s/%lu\n", v6str, mask);
+	return 0;
+}

package/6rd/src/Makefile

@@ -0,0 +1,7 @@
+all: 6rdcalc
+
+6rdcalc: 6rdcalc.c
+	$(CC) $(CFLAGS) $(LDFLAGS) -o $@ $<
+
+clean:
+	rm -f 6rdcalc