path: root/src/net/ipv6.c

/*
 * Copyright (C) 2013 Michael Brown <mbrown@fensystems.co.uk>.
 *
 * 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 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., 51 Franklin Street, Fifth Floor, Boston, MA
 * 02110-1301, USA.
 */

FILE_LICENCE ( GPL2_OR_LATER );

#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <assert.h>
#include <byteswap.h>
#include <ipxe/iobuf.h>
#include <ipxe/tcpip.h>
#include <ipxe/if_ether.h>
#include <ipxe/crc32.h>
#include <ipxe/fragment.h>
#include <ipxe/ndp.h>
#include <ipxe/ipv6.h>

/** @file
 *
 * IPv6 protocol
 *
 */

/* Disambiguate the various error causes */
#define EINVAL_LEN __einfo_error ( EINFO_EINVAL_LEN )
#define EINFO_EINVAL_LEN \
	__einfo_uniqify ( EINFO_EINVAL, 0x01, "Invalid length" )
#define ENOTSUP_VER __einfo_error ( EINFO_ENOTSUP_VER )
#define EINFO_ENOTSUP_VER \
	__einfo_uniqify ( EINFO_ENOTSUP, 0x01, "Unsupported version" )
#define ENOTSUP_HDR __einfo_error ( EINFO_ENOTSUP_HDR )
#define EINFO_ENOTSUP_HDR \
	__einfo_uniqify ( EINFO_ENOTSUP, 0x02, "Unsupported header type" )
#define ENOTSUP_OPT __einfo_error ( EINFO_ENOTSUP_OPT )
#define EINFO_ENOTSUP_OPT \
	__einfo_uniqify ( EINFO_ENOTSUP, 0x03, "Unsupported option" )

/** List of IPv6 miniroutes */
struct list_head ipv6_miniroutes = LIST_HEAD_INIT ( ipv6_miniroutes );

/**
 * Determine debugging colour for IPv6 debug messages
 *
 * @v in		IPv6 address
 * @ret col		Debugging colour (for DBGC())
 */
static uint32_t ipv6col ( struct in6_addr *in ) {
	return crc32_le ( 0, in, sizeof ( *in ) );
}

/**
 * Check if network device has a specific IPv6 address
 *
 * @v netdev		Network device
 * @v addr		IPv6 address
 * @ret has_addr	Network device has this IPv6 address
 */
int ipv6_has_addr ( struct net_device *netdev, struct in6_addr *addr ) {
	struct ipv6_miniroute *miniroute;

	list_for_each_entry ( miniroute, &ipv6_miniroutes, list ) {
		if ( ( miniroute->netdev == netdev ) &&
		     ( memcmp ( &miniroute->address, addr,
				sizeof ( miniroute->address ) ) == 0 ) ) {
			/* Found matching address */
			return 1;
		}
	}
	return 0;
}

/**
 * Check if IPv6 address is within a routing table entry's local network
 *
 * @v miniroute		Routing table entry
 * @v address		IPv6 address
 * @ret is_local	Address is within this entry's local network
 */
static int ipv6_is_local ( struct ipv6_miniroute *miniroute,
			   struct in6_addr *address ) {
	unsigned int i;

	for ( i = 0 ; i < ( sizeof ( address->s6_addr32 ) /
			    sizeof ( address->s6_addr32[0] ) ) ; i++ ) {
		if ( (( address->s6_addr32[i] ^ miniroute->address.s6_addr32[i])
		      & miniroute->prefix_mask.s6_addr32[i] ) != 0 )
			return 0;
	}
	return 1;
}

/**
 * Add IPv6 minirouting table entry
 *
 * @v netdev		Network device
 * @v address		IPv6 address
 * @v prefix_len	Prefix length
 * @v router		Router address (or NULL)
 * @ret miniroute	Routing table entry, or NULL on failure
 */
static struct ipv6_miniroute * __malloc
add_ipv6_miniroute ( struct net_device *netdev, struct in6_addr *address,
		     unsigned int prefix_len, struct in6_addr *router ) {
	struct ipv6_miniroute *miniroute;
	uint8_t *prefix_mask;

	DBGC ( netdev, "IPv6 add %s/%d ", inet6_ntoa ( address ), prefix_len );
	if ( router )
		DBGC ( netdev, "router %s ", inet6_ntoa ( router ) );
	DBGC ( netdev, "via %s\n", netdev->name );

	/* Allocate and populate miniroute structure */
	miniroute = zalloc ( sizeof ( *miniroute ) );
	if ( ! miniroute )
		return NULL;

	/* Record routing information */
	miniroute->netdev = netdev_get ( netdev );
	memcpy ( &miniroute->address, address, sizeof ( miniroute->address ) );
	miniroute->prefix_len = prefix_len;
	assert ( prefix_len <= ( 8 * sizeof ( miniroute->prefix_mask ) ) );
	for ( prefix_mask = miniroute->prefix_mask.s6_addr ; prefix_len >= 8 ;
	      prefix_mask++, prefix_len -= 8 ) {
		*prefix_mask = 0xff;
	}
	if ( prefix_len )
		*prefix_mask <<= ( 8 - prefix_len );
	if ( router ) {
		miniroute->has_router = 1;
		memcpy ( &miniroute->router, router,
			 sizeof ( miniroute->router ) );
	}

	/* Add to end of list if we have a gateway, otherwise to start
	 * of list.
	 */
	if ( router ) {
		list_add_tail ( &miniroute->list, &ipv6_miniroutes );
	} else {
		list_add ( &miniroute->list, &ipv6_miniroutes );
	}

	return miniroute;
}

/**
 * Delete IPv6 minirouting table entry
 *
 * @v miniroute		Routing table entry
 */
static void del_ipv6_miniroute ( struct ipv6_miniroute *miniroute ) {
	struct net_device *netdev = miniroute->netdev;

	DBGC ( netdev, "IPv6 del %s/%d ", inet6_ntoa ( &miniroute->address ),
	       miniroute->prefix_len );
	if ( miniroute->has_router )
		DBGC ( netdev, "router %s ", inet6_ntoa ( &miniroute->router ));
	DBGC ( netdev, "via %s\n", netdev->name );

	netdev_put ( miniroute->netdev );
	list_del ( &miniroute->list );
	free ( miniroute );
}

/**
 * Perform IPv6 routing
 *
 * @v scope_id		Destination address scope ID (for link-local addresses)
 * @v dest		Final destination address
 * @ret dest		Next hop destination address
 * @ret miniroute	Routing table entry to use, or NULL if no route
 */
static struct ipv6_miniroute * ipv6_route ( unsigned int scope_id,
					   struct in6_addr **dest ) {
	struct ipv6_miniroute *miniroute;
	int local;

	/* Find first usable route in routing table */
	list_for_each_entry ( miniroute, &ipv6_miniroutes, list ) {

		/* Skip closed network devices */
		if ( ! netdev_is_open ( miniroute->netdev ) )
			continue;

		/* For link-local addresses, skip devices that are not
		 * the specified network device.
		 */
		if ( IN6_IS_ADDR_LINKLOCAL ( *dest ) &&
		     ( miniroute->netdev->index != scope_id ) )
			continue;

		/* Skip non-gateway devices for which the prefix does
		 * not match.
		 */
		local = ipv6_is_local ( miniroute, *dest );
		if ( ! ( local || miniroute->has_router ) )
			continue;

		/* Update next hop if applicable */
		if ( ! local )
			*dest = &miniroute->router;

		return miniroute;
	}

	return NULL;
}

/**
 * Check that received options can be safely ignored
 *
 * @v iphdr		IPv6 header
 * @v options		Options extension header
 * @v len		Maximum length of header
 * @ret rc		Return status code
 */
static int ipv6_check_options ( struct ipv6_header *iphdr,
				struct ipv6_options_header *options,
				size_t len ) {
	struct ipv6_option *option = options->options;
	struct ipv6_option *end = ( ( ( void * ) options ) + len );

	while ( option < end ) {
		if ( ! IPV6_CAN_IGNORE_OPT ( option->type ) ) {
			DBGC ( ipv6col ( &iphdr->src ), "IPv6 unrecognised "
			       "option type %#02x:\n", option->type );
			DBGC_HDA ( ipv6col ( &iphdr->src ), 0,
				   options, len );
			return -ENOTSUP_OPT;
		}
		if ( option->type == IPV6_OPT_PAD1 ) {
			option = ( ( ( void * ) option ) + 1 );
		} else {
			option = ( ( ( void * ) option ) + option->len );
		}
	}
	return 0;
}

/**
 * Check if fragment matches fragment reassembly buffer
 *
 * @v fragment		Fragment reassembly buffer
 * @v iobuf		I/O buffer
 * @v hdrlen		Length of non-fragmentable potion of I/O buffer
 * @ret is_fragment	Fragment matches this reassembly buffer
 */
static int ipv6_is_fragment ( struct fragment *fragment,
			      struct io_buffer *iobuf, size_t hdrlen ) {
	struct ipv6_header *frag_iphdr = fragment->iobuf->data;
	struct ipv6_fragment_header *frag_fhdr =
		( fragment->iobuf->data + fragment->hdrlen -
		  sizeof ( *frag_fhdr ) );
	struct ipv6_header *iphdr = iobuf->data;
	struct ipv6_fragment_header *fhdr =
		( iobuf->data + hdrlen - sizeof ( *fhdr ) );

	return ( ( memcmp ( &iphdr->src, &frag_iphdr->src,
			    sizeof ( iphdr->src ) ) == 0 ) &&
		 ( fhdr->ident == frag_fhdr->ident ) );
}

/**
 * Get fragment offset
 *
 * @v iobuf		I/O buffer
 * @v hdrlen		Length of non-fragmentable potion of I/O buffer
 * @ret offset		Offset
 */
static size_t ipv6_fragment_offset ( struct io_buffer *iobuf, size_t hdrlen ) {
	struct ipv6_fragment_header *fhdr =
		( iobuf->data + hdrlen - sizeof ( *fhdr ) );

	return ( ntohs ( fhdr->offset_more ) & IPV6_MASK_OFFSET );
}

/**
 * Check if more fragments exist
 *
 * @v iobuf		I/O buffer
 * @v hdrlen		Length of non-fragmentable potion of I/O buffer
 * @ret more_frags	More fragments exist
 */
static int ipv6_more_fragments ( struct io_buffer *iobuf, size_t hdrlen ) {
	struct ipv6_fragment_header *fhdr =
		( iobuf->data + hdrlen - sizeof ( *fhdr ) );

	return ( fhdr->offset_more & htons ( IPV6_MASK_MOREFRAGS ) );
}

/** Fragment reassembler */
static struct fragment_reassembler ipv6_reassembler = {
	.list = LIST_HEAD_INIT ( ipv6_reassembler.list ),
	.is_fragment = ipv6_is_fragment,
	.fragment_offset = ipv6_fragment_offset,
	.more_fragments = ipv6_more_fragments,
};

/**
 * Calculate IPv6 pseudo-header checksum
 *
 * @v iphdr		IPv6 header
 * @v len		Payload length
 * @v next_header	Next header type
 * @v csum		Existing checksum
 * @ret csum		Updated checksum
 */
static uint16_t ipv6_pshdr_chksum ( struct ipv6_header *iphdr, size_t len,
				    int next_header, uint16_t csum ) {
	struct ipv6_pseudo_header pshdr;

	/* Build pseudo-header */
	memcpy ( &pshdr.src, &iphdr->src, sizeof ( pshdr.src ) );
	memcpy ( &pshdr.dest, &iphdr->dest, sizeof ( pshdr.dest ) );
	pshdr.len = htonl ( len );
	memset ( pshdr.zero, 0, sizeof ( pshdr.zero ) );
	pshdr.next_header = next_header;

	/* Update the checksum value */
	return tcpip_continue_chksum ( csum, &pshdr, sizeof ( pshdr ) );
}

/**
 * Transmit IPv6 packet
 *
 * @v iobuf		I/O buffer
 * @v tcpip		Transport-layer protocol
 * @v st_src		Source network-layer address
 * @v st_dest		Destination network-layer address
 * @v netdev		Network device to use if no route found, or NULL
 * @v trans_csum	Transport-layer checksum to complete, or NULL
 * @ret rc		Status
 *
 * This function expects a transport-layer segment and prepends the
 * IPv6 header
 */
static int ipv6_tx ( struct io_buffer *iobuf,
		     struct tcpip_protocol *tcpip_protocol,
		     struct sockaddr_tcpip *st_src,
		     struct sockaddr_tcpip *st_dest,
		     struct net_device *netdev,
		     uint16_t *trans_csum ) {
	struct sockaddr_in6 *sin6_src = ( ( struct sockaddr_in6 * ) st_src );
	struct sockaddr_in6 *sin6_dest = ( ( struct sockaddr_in6 * ) st_dest );
	struct ipv6_miniroute *miniroute;
	struct ipv6_header *iphdr;
	struct in6_addr *next_hop;
	uint8_t ll_dest_buf[MAX_LL_ADDR_LEN];
	const void *ll_dest;
	size_t len;
	int rc;

	/* Fill up the IPv6 header, except source address */
	len = iob_len ( iobuf );
	iphdr = iob_push ( iobuf, sizeof ( *iphdr ) );
	memset ( iphdr, 0, sizeof ( *iphdr ) );
	iphdr->ver_tc_label = htonl ( IPV6_VER );
	iphdr->len = htons ( len );
	iphdr->next_header = tcpip_protocol->tcpip_proto;
	iphdr->hop_limit = IPV6_HOP_LIMIT;
	memcpy ( &iphdr->dest, &sin6_dest->sin6_addr, sizeof ( iphdr->dest ) );

	/* Use routing table to identify next hop and transmitting netdev */
	next_hop = &iphdr->dest;
	if ( sin6_src ) {
		memcpy ( &iphdr->src, &sin6_src->sin6_addr,
			 sizeof ( iphdr->src ) );
	}
	if ( ( ! IN6_IS_ADDR_MULTICAST ( next_hop ) ) &&
	     ( ( miniroute = ipv6_route ( ntohl ( sin6_dest->sin6_scope_id ),
					  &next_hop ) ) != NULL ) ) {
		memcpy ( &iphdr->src, &miniroute->address,
			 sizeof ( iphdr->src ) );
		netdev = miniroute->netdev;
	}
	if ( ! netdev ) {
		DBGC ( ipv6col ( &iphdr->dest ), "IPv6 has no route to %s\n",
		       inet6_ntoa ( &iphdr->dest ) );
		rc = -ENETUNREACH;
		goto err;
	}

	/* Fix up checksums */
	if ( trans_csum ) {
		*trans_csum = ipv6_pshdr_chksum ( iphdr, len,
						  tcpip_protocol->tcpip_proto,
						  *trans_csum );
	}

	/* Print IPv6 header for debugging */
	DBGC2 ( ipv6col ( &iphdr->dest ), "IPv6 TX %s->",
		inet6_ntoa ( &iphdr->src ) );
	DBGC2 ( ipv6col ( &iphdr->dest ), "%s len %zd next %d\n",
		inet6_ntoa ( &iphdr->dest ), len, iphdr->next_header );

	/* Calculate link-layer destination address, if possible */
	if ( IN6_IS_ADDR_MULTICAST ( next_hop ) ) {
		/* Multicast address */
		if ( ( rc = netdev->ll_protocol->mc_hash ( AF_INET6, next_hop,
							   ll_dest_buf ) ) !=0){
			DBGC ( ipv6col ( &iphdr->dest ), "IPv6 could not hash "
			       "multicast %s: %s\n", inet6_ntoa ( next_hop ),
			       strerror ( rc ) );
			goto err;
		}
		ll_dest = ll_dest_buf;
	} else {
		/* Unicast address */
		ll_dest = NULL;
	}

	/* Hand off to link layer (via NDP if applicable) */
	if ( ll_dest ) {
		if ( ( rc = net_tx ( iobuf, netdev, &ipv6_protocol, ll_dest,
				     netdev->ll_addr ) ) != 0 ) {
			DBGC ( ipv6col ( &iphdr->dest ), "IPv6 could not "
			       "transmit packet via %s: %s\n",
			       netdev->name, strerror ( rc ) );
			return rc;
		}
	} else {
		if ( ( rc = ndp_tx ( iobuf, netdev, next_hop, &iphdr->src,
				     netdev->ll_addr ) ) != 0 ) {
			DBGC ( ipv6col ( &iphdr->dest ), "IPv6 could not "
			       "transmit packet via %s: %s\n",
			       netdev->name, strerror ( rc ) );
			return rc;
		}
	}

	return 0;

 err:
	free_iob ( iobuf );
	return rc;
}

/**
 * Process incoming IPv6 packets
 *
 * @v iobuf		I/O buffer
 * @v netdev		Network device
 * @v ll_dest		Link-layer destination address
 * @v ll_source		Link-layer destination source
 * @v flags		Packet flags
 * @ret rc		Return status code
 *
 * This function expects an IPv6 network datagram. It processes the
 * headers and sends it to the transport layer.
 */
static int ipv6_rx ( struct io_buffer *iobuf, struct net_device *netdev,
		     const void *ll_dest __unused,
		     const void *ll_source __unused,
		     unsigned int flags __unused ) {
	struct ipv6_header *iphdr = iobuf->data;
	union ipv6_extension_header *ext;
	union {
		struct sockaddr_in6 sin6;
		struct sockaddr_tcpip st;
	} src, dest;
	uint16_t pshdr_csum;
	size_t len;
	size_t hdrlen;
	size_t extlen;
	int this_header;
	int next_header;
	int rc;

	/* Sanity check the IPv6 header */
	if ( iob_len ( iobuf ) < sizeof ( *iphdr ) ) {
		DBGC ( ipv6col ( &iphdr->src ), "IPv6 packet too short at %zd "
		       "bytes (min %zd bytes)\n", iob_len ( iobuf ),
		       sizeof ( *iphdr ) );
		rc = -EINVAL_LEN;
		goto err;
	}
	if ( ( iphdr->ver_tc_label & htonl ( IPV6_MASK_VER ) ) !=
	     htonl ( IPV6_VER ) ) {
		DBGC ( ipv6col ( &iphdr->src ), "IPv6 version %#08x not "
		       "supported\n", ntohl ( iphdr->ver_tc_label ) );
		rc = -ENOTSUP_VER;
		goto err;
	}

	/* Truncate packet to specified length */
	len = ntohs ( iphdr->len );
	if ( len > iob_len ( iobuf ) ) {
		DBGC ( ipv6col ( &iphdr->src ), "IPv6 length too long at %zd "
		       "bytes (packet is %zd bytes)\n", len, iob_len ( iobuf ));
		rc = -EINVAL_LEN;
		goto err;
	}
	iob_unput ( iobuf, ( iob_len ( iobuf ) - len - sizeof ( *iphdr ) ) );
	hdrlen = sizeof ( *iphdr );

	/* Print IPv6 header for debugging */
	DBGC2 ( ipv6col ( &iphdr->src ), "IPv6 RX %s<-",
		inet6_ntoa ( &iphdr->dest ) );
	DBGC2 ( ipv6col ( &iphdr->src ), "%s len %zd next %d\n",
		inet6_ntoa ( &iphdr->src ), len, iphdr->next_header );

	/* Discard unicast packets not destined for us */
	if ( ( ! ( flags & LL_MULTICAST ) ) &&
	     ( ! ipv6_has_addr ( netdev, &iphdr->dest ) ) ) {
		DBGC ( ipv6col ( &iphdr->src ), "IPv6 discarding non-local "
		       "unicast packet for %s\n", inet6_ntoa ( &iphdr->dest ) );
		rc = -EPIPE;
		goto err;
	}

	/* Process any extension headers */
	next_header = iphdr->next_header;
	while ( 1 ) {

		/* Extract extension header */
		this_header = next_header;
		ext = ( iobuf->data + hdrlen );
		extlen = sizeof ( ext->pad );
		if ( iob_len ( iobuf ) < ( hdrlen + extlen ) ) {
			DBGC ( ipv6col ( &iphdr->src ), "IPv6 too short for "
			       "extension header type %d at %zd bytes (min "
			       "%zd bytes)\n", this_header,
			       ( iob_len ( iobuf ) - hdrlen ), extlen );
			rc = -EINVAL_LEN;
			goto err;
		}

		/* Determine size of extension header (if applicable) */
		if ( ( this_header == IPV6_HOPBYHOP ) ||
		     ( this_header == IPV6_DESTINATION ) ||
		     ( this_header == IPV6_ROUTING ) ) {
			/* Length field is present */
			extlen += ext->common.len;
		} else if ( this_header == IPV6_FRAGMENT ) {
			/* Length field is reserved and ignored (RFC2460) */
		} else {
			/* Not an extension header; assume rest is payload */
			break;
		}
		if ( iob_len ( iobuf ) < ( hdrlen + extlen ) ) {
			DBGC ( ipv6col ( &iphdr->src ), "IPv6 too short for "
			       "extension header type %d at %zd bytes (min "
			       "%zd bytes)\n", this_header,
			       ( iob_len ( iobuf ) - hdrlen ), extlen );
			rc = -EINVAL_LEN;
			goto err;
		}
		hdrlen += extlen;
		next_header = ext->common.next_header;
		DBGC2 ( ipv6col ( &iphdr->src ), "IPv6 RX %s<-",
			inet6_ntoa ( &iphdr->dest ) );
		DBGC2 ( ipv6col ( &iphdr->src ), "%s ext type %d len %zd next "
			"%d\n", inet6_ntoa ( &iphdr->src ), this_header,
			extlen, next_header );

		/* Process this extension header */
		if ( ( this_header == IPV6_HOPBYHOP ) ||
		     ( this_header == IPV6_DESTINATION ) ) {

			/* Check that all options can be ignored */
			if ( ( rc = ipv6_check_options ( iphdr, &ext->options,
							 extlen ) ) != 0 )
				goto err;

		} else if ( this_header == IPV6_FRAGMENT ) {

			/* Reassemble fragments */
			iobuf = fragment_reassemble ( &ipv6_reassembler, iobuf,
						      &hdrlen );
			if ( ! iobuf )
				return 0;
			iphdr = iobuf->data;
		}
	}

	/* Construct socket address, calculate pseudo-header checksum,
	 * and hand off to transport layer
	 */
	memset ( &src, 0, sizeof ( src ) );
	src.sin6.sin6_family = AF_INET6;
	memcpy ( &src.sin6.sin6_addr, &iphdr->src,
		 sizeof ( src.sin6.sin6_addr ) );
	src.sin6.sin6_scope_id = htonl ( netdev->index );
	memset ( &dest, 0, sizeof ( dest ) );
	dest.sin6.sin6_family = AF_INET6;
	memcpy ( &dest.sin6.sin6_addr, &iphdr->dest,
		 sizeof ( dest.sin6.sin6_addr ) );
	dest.sin6.sin6_scope_id = htonl ( netdev->index );
	iob_pull ( iobuf, hdrlen );
	pshdr_csum = ipv6_pshdr_chksum ( iphdr, iob_len ( iobuf ),
					 next_header, TCPIP_EMPTY_CSUM );
	if ( ( rc = tcpip_rx ( iobuf, netdev, next_header, &src.st, &dest.st,
			       pshdr_csum ) ) != 0 ) {
		DBGC ( ipv6col ( &src.sin6.sin6_addr ), "IPv6 received packet "
				"rejected by stack: %s\n", strerror ( rc ) );
		return rc;
	}

	return 0;

 err:
	free_iob ( iobuf );
	return rc;
}

/**
 * Convert IPv6 address to standard notation
 *
 * @v in	IPv6 address
 * @ret string	IPv6 address in standard notation
 *
 * RFC5952 defines the canonical format for IPv6 textual representation.
 */
char * inet6_ntoa ( const struct in6_addr *in ) {
	static char buf[41]; /* ":xxxx:xxxx:xxxx:xxxx:xxxx:xxxx:xxxx:xxxx" */
	char *out = buf;
	char *longest_start = NULL;
	char *start = NULL;
	int longest_len = 1;
	int len = 0;
	char *dest;
	unsigned int i;
	uint16_t value;

	/* Format address, keeping track of longest run of zeros */
	for ( i = 0 ; i < ( sizeof ( in->s6_addr16 ) /
			    sizeof ( in->s6_addr16[0] ) ) ; i++ ) {
		value = ntohs ( in->s6_addr16[i] );
		if ( value == 0 ) {
			if ( len++ == 0 )
				start = out;
			if ( len > longest_len ) {
				longest_start = start;
				longest_len = len;
			}
		} else {
			len = 0;
		}
		out += sprintf ( out, ":%x", value );
	}

	/* Abbreviate longest run of zeros, if applicable */
	if ( longest_start ) {
		dest = strcpy ( ( longest_start + 1 ),
				( longest_start + ( 2 * longest_len ) ) );
		if ( dest[0] == '\0' )
			dest[1] = '\0';
		dest[0] = ':';
	}
	return ( ( longest_start == buf ) ? buf : ( buf + 1 ) );
}

/**
 * Transcribe IPv6 address
 *
 * @v net_addr	IPv6 address
 * @ret string	IPv6 address in standard notation
 *
 */
static const char * ipv6_ntoa ( const void *net_addr ) {
	return inet6_ntoa ( net_addr );
}

/** IPv6 protocol */
struct net_protocol ipv6_protocol __net_protocol = {
	.name = "IPv6",
	.net_proto = htons ( ETH_P_IPV6 ),
	.net_addr_len = sizeof ( struct in6_addr ),
	.rx = ipv6_rx,
	.ntoa = ipv6_ntoa,
};

/** IPv6 TCPIP net protocol */
struct tcpip_net_protocol ipv6_tcpip_protocol __tcpip_net_protocol = {
	.name = "IPv6",
	.sa_family = AF_INET6,
	.tx = ipv6_tx,
};

/**
 * Create IPv6 network device
 *
 * @v netdev		Network device
 * @ret rc		Return status code
 */
static int ipv6_probe ( struct net_device *netdev ) {
	struct ipv6_miniroute *miniroute;
	struct in6_addr address;
	int prefix_len;
	int rc;

	/* Construct link-local address from EUI-64 as per RFC 2464 */
	prefix_len = ipv6_link_local ( &address, netdev );
	if ( prefix_len < 0 ) {
		rc = prefix_len;
		DBGC ( netdev, "IPv6 %s could not construct link-local "
		       "address: %s\n", netdev->name, strerror ( rc ) );
		return rc;
	}

	/* Create link-local address for this network device */
	miniroute = add_ipv6_miniroute ( netdev, &address, prefix_len, NULL );
	if ( ! miniroute )
		return -ENOMEM;

	return 0;
}

/**
 * Handle IPv6 network device or link state change
 *
 * @v netdev		Network device
 */
static void ipv6_notify ( struct net_device *netdev __unused ) {

	/* Nothing to do */
}

/**
 * Destroy IPv6 network device
 *
 * @v netdev		Network device
 */
static void ipv6_remove ( struct net_device *netdev ) {
	struct ipv6_miniroute *miniroute;
	struct ipv6_miniroute *tmp;

	/* Delete all miniroutes for this network device */
	list_for_each_entry_safe ( miniroute, tmp, &ipv6_miniroutes, list ) {
		if ( miniroute->netdev == netdev )
			del_ipv6_miniroute ( miniroute );
	}
}

/** IPv6 network device driver */
struct net_driver ipv6_driver __net_driver = {
	.name = "IPv6",
	.probe = ipv6_probe,
	.notify = ipv6_notify,
	.remove = ipv6_remove,
};

/* Drag in ICMPv6 */
REQUIRE_OBJECT ( icmpv6 );

/* Drag in NDP */
REQUIRE_OBJECT ( ndp );