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incubator-nuttx/net/ipforward/ipv6_forward.c

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/****************************************************************************
* net/ipforward/ipv6_forward.c
*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership. The
* ASF licenses this file to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance with the
* License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
* License for the specific language governing permissions and limitations
* under the License.
*
****************************************************************************/
/****************************************************************************
* Included Files
****************************************************************************/
#include <nuttx/config.h>
#include <string.h>
#include <assert.h>
#include <errno.h>
#include <debug.h>
#include <nuttx/mm/iob.h>
#include <nuttx/net/ipv6ext.h>
#include <nuttx/net/net.h>
#include <nuttx/net/netdev.h>
#include <nuttx/net/netstats.h>
#include "netdev/netdev.h"
#include "sixlowpan/sixlowpan.h"
#include "devif/devif.h"
#include "icmpv6/icmpv6.h"
#include "ipforward/ipforward.h"
#if defined(CONFIG_NET_IPFORWARD) && defined(CONFIG_NET_IPv6)
/****************************************************************************
* Pre-processor Definitions
****************************************************************************/
#define PACKET_FORWARDED 0
#define PACKET_NOT_FORWARDED 1
/****************************************************************************
* Private Functions
****************************************************************************/
/****************************************************************************
* Name: ipv6_hdrsize
*
* Description:
* Return the size of the IPv6 header and the following.
*
* Input Parameters:
* ipv6 - A pointer to the IPv6 header in within the IPv6 packet. This
* is immediately followed by the L3 header which may be TCP, UDP,
* or ICMPv6.
*
* Returned Value:
* The size of the combined L2 + L3 headers is returned on success. An
* error is returned only if the prototype is not supported.
*
****************************************************************************/
#ifdef CONFIG_DEBUG_NET_WARN
static int ipv6_hdrsize(FAR struct ipv6_hdr_s *ipv6)
{
/* Size is determined by the following protocol header, */
switch (ipv6->proto)
{
#ifdef CONFIG_NET_TCP
case IP_PROTO_TCP:
{
FAR struct tcp_hdr_s *tcp =
(FAR struct tcp_hdr_s *)((FAR uint8_t *)ipv6 + IPv6_HDRLEN);
unsigned int tcpsize;
/* The TCP header length is encoded in the top 4 bits of the
* tcpoffset field (in units of 32-bit words).
*/
tcpsize = ((uint16_t)tcp->tcpoffset >> 4) << 2;
return IPv6_HDRLEN + tcpsize;
}
break;
#endif
#ifdef CONFIG_NET_UDP
case IP_PROTO_UDP:
return IPv6_HDRLEN + UDP_HDRLEN;
break;
#endif
#ifdef CONFIG_NET_ICMPv6
case IP_PROTO_ICMP6:
return IPv6_HDRLEN + ICMPv6_HDRLEN;
break;
#endif
#ifdef CONFIG_NET_IPFRAG
case NEXT_FRAGMENT_EH:
return IPv6_HDRLEN + EXTHDR_FRAG_LEN;
break;
#endif
default:
nwarn("WARNING: Unrecognized proto: %u\n", ipv6->proto);
return -EPROTONOSUPPORT;
}
}
#endif
/****************************************************************************
* Name: ipv6_decr_ttl
*
* Description:
* Decrement the IPv6 TTL (time to live value). TTL field is set by the
* sender of the packet and reduced by every router on the route to its
* destination. If the TTL field reaches zero before the datagram arrives
* at its destination, then the datagram is discarded and an ICMP error
* packet (11 - Time Exceeded) is sent back to the sender.
*
* The purpose of the TTL field is to avoid a situation in which an
* undeliverable datagram keeps circulating on an Internet system, and
* such a system eventually becoming swamped by such "immortals".
*
* Input Parameters:
* ipv6 - A pointer to the IPv6 header in within the IPv6 packet to be
* forwarded.
*
* Returned Value:
* The new TTL value is returned. A value <= 0 means the hop limit has
* expired.
*
****************************************************************************/
static int ipv6_decr_ttl(FAR struct ipv6_hdr_s *ipv6)
{
int ttl = (int)ipv6->ttl - 1;
if (ttl <= 0)
{
/* Return zero which must cause the packet to be dropped */
return 0;
}
/* Save the updated TTL value */
ipv6->ttl = ttl;
/* NOTE: We do not have to recalculate the IPv6 checksum because (1) the
* IPv6 header does not include a checksum itself and (2) the TTL is not
* included in the sum for the TCP and UDP headers.
*/
return ttl;
}
/****************************************************************************
* Name: ipv6_packet_conversion
*
* Description:
* Generic output conversion hook. Only needed for IEEE802.15.4 for now
* but this is a point where support for other conversions may be
* provided.
*
* Returned Value:
* PACKET_FORWARDED - Packet was forwarded
* PACKET_NOT_FORWARDED - Packet was not forwarded
* < 0 - And error occurred (and packet not forwarded).
*
****************************************************************************/
#ifdef CONFIG_NET_6LOWPAN
static int ipv6_packet_conversion(FAR struct net_driver_s *dev,
FAR struct net_driver_s *fwddev,
FAR struct ipv6_hdr_s *ipv6)
{
int ret = PACKET_NOT_FORWARDED;
if (dev->d_len > 0)
{
/* Check if this is a device served by 6LoWPAN */
if (fwddev->d_lltype != NET_LL_IEEE802154 &&
fwddev->d_lltype != NET_LL_PKTRADIO)
{
nwarn("WARNING: Unsupported link layer... Not forwarded\n");
}
else
#ifdef CONFIG_NET_TCP
if (ipv6->proto == IP_PROTO_TCP)
{
/* Decrement the TTL in the IPv6 header. If it decrements to
* zero, then drop the packet.
*/
ret = ipv6_decr_ttl(ipv6);
if (ret < 1)
{
nwarn("WARNING: Hop limit exceeded... Dropping!\n");
ret = -EMULTIHOP;
}
else
{
/* Let 6LoWPAN convert IPv6 TCP output into IEEE802.15.4
* frames.
*/
sixlowpan_tcp_send(dev, fwddev, ipv6);
/* The packet was forwarded */
dev->d_len = 0;
return PACKET_FORWARDED;
}
}
else
#endif
#ifdef CONFIG_NET_UDP
if (ipv6->proto == IP_PROTO_UDP)
{
/* Decrement the TTL in the IPv6 header. If it decrements to
* zero, then drop the packet.
*/
ret = ipv6_decr_ttl(ipv6);
if (ret < 1)
{
nwarn("WARNING: Hop limit exceeded... Dropping!\n");
ret = -EMULTIHOP;
}
else
{
/* Let 6LoWPAN convert IPv6 UDP output into IEEE802.15.4
* frames.
*/
sixlowpan_udp_send(dev, fwddev, ipv6);
/* The packet was forwarded */
dev->d_len = 0;
return PACKET_FORWARDED;
}
}
else
#endif
#ifdef CONFIG_NET_ICMPv6
if (ipv6->proto == IP_PROTO_ICMP6)
{
/* Decrement the TTL in the IPv6 header. If it decrements to
* zero, then drop the packet.
*/
ret = ipv6_decr_ttl(ipv6);
if (ret < 1)
{
nwarn("WARNING: Hop limit exceeded... Dropping!\n");
ret = -EMULTIHOP;
}
else
{
/* Let 6LoWPAN convert IPv6 ICMPv6 output into IEEE802.15.4
* frames.
*/
sixlowpan_icmpv6_send(dev, fwddev, ipv6);
/* The packet was forwarded */
dev->d_len = 0;
return PACKET_FORWARDED;
}
}
else
#endif
{
/* Otherwise, we cannot forward the packet */
nwarn("WARNING: Dropping. Unsupported 6LoWPAN protocol: %d\n",
ipv6->proto);
}
}
/* The packet was not forwarded (or the HOP limit was exceeded) */
ipv6_dropstats(ipv6);
return ret;
}
#else
# define ipv6_packet_conversion(dev, fwddev, ipv6) (PACKET_NOT_FORWARDED)
#endif /* CONFIG_NET_6LOWPAN */
/****************************************************************************
* Name: ipv6_dev_forward
*
* Description:
* This function is called from ipv6_forward when it is necessary to
* forward a packet from the current device to different device. In this
* case, the forwarding operation must be performed asynchronously when
* the TX poll is received from the forwarding device.
*
* Input Parameters:
* dev - The device on which the packet was received and which
* contains the IPv6 packet.
* fwdddev - The device on which the packet must be forwarded.
* ipv6 - A pointer to the IPv6 header in within the IPv6 packet
*
* Returned Value:
* Zero is returned if the packet was successfully forwarded; A negated
* errno value is returned if the packet is not forwardable. In that
* latter case, the caller (ipv6_input()) should drop the packet.
*
****************************************************************************/
static int ipv6_dev_forward(FAR struct net_driver_s *dev,
FAR struct net_driver_s *fwddev,
FAR struct ipv6_hdr_s *ipv6)
{
FAR struct forward_s *fwd = NULL;
#ifdef CONFIG_DEBUG_NET_WARN
int hdrsize;
#endif
int ret;
/* If the interface isn't "up", we can't forward. */
if ((fwddev->d_flags & IFF_UP) == 0)
{
nwarn("WARNING: device is DOWN\n");
ret = -EHOSTUNREACH;
goto errout;
}
/* Perform any necessary packet conversions. */
ret = ipv6_packet_conversion(dev, fwddev, ipv6);
if (ret < 0)
{
nwarn("WARNING: ipv6_packet_conversion failed: %d\n", ret);
goto errout;
}
else if (ret == PACKET_NOT_FORWARDED)
{
/* Verify that the full packet will fit within the forwarding devices
* MTU. We provide no support for fragmenting forwarded packets.
*/
if (NET_LL_HDRLEN(fwddev) + dev->d_len > NETDEV_PKTSIZE(fwddev))
{
nwarn("WARNING: Packet > MTU... Dropping\n");
ret = -EFBIG;
goto errout;
}
/* Get a pre-allocated forwarding structure, This structure will be
* completely zeroed when we receive it.
*/
fwd = ipfwd_alloc();
if (fwd == NULL)
{
nwarn("WARNING: Failed to allocate forwarding structure\n");
ret = -ENOMEM;
goto errout;
}
/* Initialize the easy stuff in the forwarding structure */
fwd->f_dev = fwddev; /* Forwarding device */
#ifdef CONFIG_NET_IPv4
fwd->f_domain = PF_INET6; /* IPv6 address domain */
#endif
#ifdef CONFIG_DEBUG_NET_WARN
/* Get the size of the IPv6 + L3 header. */
hdrsize = ipv6_hdrsize(ipv6);
if (hdrsize < IPv6_HDRLEN)
{
nwarn("WARNING: Could not determine L2+L3 header size\n");
ret = -EPROTONOSUPPORT;
goto errout_with_fwd;
}
/* The L2/L3 headers must fit within one, contiguous IOB. */
if (hdrsize > CONFIG_IOB_BUFSIZE)
{
nwarn("WARNING: Header is too big for pre-allocated structure\n");
ret = -E2BIG;
goto errout_with_fwd;
}
#endif
/* Relay the device buffer */
fwd->f_iob = dev->d_iob;
/* Decrement the TTL in the copy of the IPv6 header (retaining the
* original TTL in the sourcee to handle the broadcast case). If the
* TTL decrements to zero, then do not forward the packet.
*/
ret = ipv6_decr_ttl(ipv6);
if (ret < 1)
{
nwarn("WARNING: Hop limit exceeded... Dropping!\n");
ret = -EMULTIHOP;
goto errout_with_fwd;
}
/* Then set up to forward the packet according to the protocol. */
ret = ipfwd_forward(fwd);
if (ret >= 0)
{
netdev_iob_clear(dev);
return OK;
}
}
errout_with_fwd:
if (fwd != NULL)
{
ipfwd_free(fwd);
}
errout:
return ret;
}
/****************************************************************************
* Name: ipv6_forward_callback
*
* Description:
* This function is a callback from netdev_foreach. It implements the
* the broadcast forwarding action for each network device (other than, of
* course, the device that received the packet).
*
* Input Parameters:
* dev - The device on which the packet was received and which contains
* the IPv6 packet.
* ipv6 - A convenience pointer to the IPv6 header in within the IPv6
* packet
*
* Returned Value:
* Typically returns zero (meaning to continue the enumeration), but will
* return a non-zero to stop the enumeration if an error occurs.
*
****************************************************************************/
#ifdef CONFIG_NET_IPFORWARD_BROADCAST
static int ipv6_forward_callback(FAR struct net_driver_s *fwddev,
FAR void *arg)
{
FAR struct net_driver_s *dev = (FAR struct net_driver_s *)arg;
FAR struct ipv6_hdr_s *ipv6;
FAR struct iob_s *iob;
int ret;
DEBUGASSERT(fwddev != NULL);
/* Only IFF_UP device and non-loopback device need forward packet */
if (!IFF_IS_UP(fwddev->d_flags) || fwddev->d_lltype == NET_LL_LOOPBACK)
{
return OK;
}
DEBUGASSERT(dev != NULL && dev->d_buf != NULL);
/* Check if we are forwarding on the same device that we received the
* packet from.
*/
if (fwddev != dev)
{
/* Backup the forward IP packet */
iob = iob_tryalloc(true);
if (iob == NULL)
{
nerr("ERROR: iob alloc failed when forward broadcast\n");
return -ENOMEM;
}
iob_reserve(iob, CONFIG_NET_LL_GUARDSIZE);
ret = iob_clone_partial(dev->d_iob, dev->d_iob->io_pktlen, 0,
iob, 0, true, false);
if (ret < 0)
{
iob_free_chain(iob);
return ret;
}
/* Recover the pointer to the IPv6 header in the receiving device's
* d_buf.
*/
ipv6 = IPv6BUF;
/* Send the packet asynchrously on the forwarding device. */
ret = ipv6_dev_forward(dev, fwddev, ipv6);
if (ret < 0)
{
iob_free_chain(iob);
nwarn("WARNING: ipv6_dev_forward failed: %d\n", ret);
return ret;
}
/* Restore device iob with backup iob */
netdev_iob_replace(dev, iob);
}
return OK;
}
#endif
/****************************************************************************
* Public Functions
****************************************************************************/
/****************************************************************************
* Name: ipv6_forward
*
* Description:
* This function is called from ipv6_input when a packet is received that
* is not destined for us. In this case, the packet may need to be
* forwarded to another device (or sent back out the same device)
* depending configuration, routing table information, and the IPv6
* networks served by various network devices.
*
* Input Parameters:
* dev - The device on which the packet was received and which contains
* the IPv6 packet.
* ipv6 - A convenience pointer to the IPv6 header in within the IPv6
* packet
*
* On input:
* - dev->d_buf holds the received packet.
* - dev->d_len holds the length of the received packet MINUS the
* size of the L1 header. That was subtracted out by ipv6_input.
* - ipv6 points to the IPv6 header with dev->d_buf.
*
* Returned Value:
* Zero is returned if the packet was successfully forward; A negated
* errno value is returned if the packet is not forwardable. In that
* latter case, the caller (ipv6_input()) should drop the packet.
*
****************************************************************************/
int ipv6_forward(FAR struct net_driver_s *dev, FAR struct ipv6_hdr_s *ipv6)
{
FAR struct net_driver_s *fwddev;
int ret;
/* Search for a device that can forward this packet. */
fwddev = netdev_findby_ripv6addr(ipv6->srcipaddr, ipv6->destipaddr);
if (fwddev == NULL)
{
nwarn("WARNING: Not routable\n");
ret = -ENETUNREACH;
goto drop;
}
/* Check if we are forwarding on the same device that we received the
* packet from.
*/
if (fwddev != dev)
{
/* Send the packet asynchrously on the forwarding device. */
ret = ipv6_dev_forward(dev, fwddev, ipv6);
if (ret < 0)
{
nwarn("WARNING: ipv6_dev_forward failed: %d\n", ret);
goto drop;
}
}
else
#if defined(CONFIG_NET_6LOWPAN) /* REVISIT: Currently only support for 6LoWPAN */
{
/* Single network device. The use case here is where an endpoint acts
* as a hub in a star configuration. This is typical for a wireless
* star configuration where not all endpoints are accessible from all
* other endpoints, but seems less useful for a wired network.
*/
/* Perform any necessary packet conversions. If the packet was handled
* via a backdoor path (or dropped), then dev->d_len will be zero. If
* the packet needs to be forwarded in the normal manner then
* dev->d_len will be unchanged.
*/
ret = ipv6_packet_conversion(dev, dev, ipv6);
if (ret < 0)
{
nwarn("WARNING: ipv6_packet_conversion failed: %d\n", ret);
goto drop;
}
else if (ret == PACKET_NOT_FORWARDED)
{
#ifdef CONFIG_NET_ETHERNET
/* REVISIT:
* For Ethernet we may have to fix up the Ethernet header:
* - source MAC, the MAC of the current device.
* - dest MAC, the MAC associated with the destination IPv6
* address.
* This will involve ICMPv6 and Neighbor Discovery.
*/
/* Correct dev->d_buf by adding back the L1 header length */
#endif
/* Nothing other 6LoWPAN forwarding is currently handled and that
* case was dealt with in ipv6_packet_conversion().
*
* REVISIT: Is this an issue? Do other use cases make sense?
*/
nwarn("WARNING: Packet forwarding supported only for 6LoWPAN\n");
ret = -ENOSYS;
goto drop;
}
}
#else /* CONFIG_NET_6LOWPAN */
{
nwarn(
"WARNING: Packet forwarding not supported in this configuration\n");
ret = -ENOSYS;
goto drop;
}
#endif /* CONFIG_NET_6LOWPAN */
/* Return success. ipv6_input will return to the network driver with
* dev->d_len set to the packet size and the network driver will perform
* the transfer.
*/
return OK;
drop:
ipv6_dropstats(ipv6);
#ifdef CONFIG_NET_ICMPv6
/* Try reply ICMPv6 to the sender. */
switch (ret)
{
case -ENETUNREACH:
icmpv6_reply(dev, ICMPv6_DEST_UNREACHABLE, ICMPv6_ADDR_UNREACH, 0);
return OK;
case -EFBIG:
icmpv6_reply(dev, ICMPv6_PACKET_TOO_BIG, 0,
NETDEV_PKTSIZE(fwddev) - NET_LL_HDRLEN(fwddev));
return OK;
case -EMULTIHOP:
icmpv6_reply(dev, ICMPv6_PACKET_TIME_EXCEEDED, ICMPV6_EXC_HOPLIMIT,
0);
return OK;
default:
break; /* We don't know how to reply, just go on (to drop). */
}
#endif
dev->d_len = 0;
return ret;
}
/****************************************************************************
* Name: ipv6_forward_broadcast
*
* Description:
* This function is called from ipv6_input when a broadcast or multicast
* packet is received. If CONFIG_NET_IPFORWARD_BROADCAST is enabled, this
* function will forward the broadcast packet to other networks through
* other network devices.
*
* Input Parameters:
* dev - The device on which the packet was received and which contains
* the IPv6 packet.
* ipv6 - A convenience pointer to the IPv6 header in within the IPv6
* packet
*
* On input:
* - dev->d_buf holds the received packet.
* - dev->d_len holds the length of the received packet MINUS the
* size of the L1 header. That was subtracted out by ipv6_input.
* - ipv6 points to the IPv6 header with dev->d_buf.
*
* Returned Value:
* None
*
****************************************************************************/
#ifdef CONFIG_NET_IPFORWARD_BROADCAST
void ipv6_forward_broadcast(FAR struct net_driver_s *dev,
FAR struct ipv6_hdr_s *ipv6)
{
/* Don't bother if the TTL would expire */
if (ipv6->ttl > 1)
{
/* Forward the the broadcast/multicast packet to all devices except,
* of course, the device that received the packet.
*/
netdev_foreach(ipv6_forward_callback, dev);
}
}
#endif
#endif /* CONFIG_NET_IPFORWARD && CONFIG_NET_IPv6 */
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