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incubator-nuttx/net/ipforward/ipv4_forward.c

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/****************************************************************************
* net/ipforward/ipv4_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 <debug.h>
#include <errno.h>
#include <nuttx/mm/iob.h>
#include <nuttx/net/net.h>
#include <nuttx/net/netdev.h>
#include <nuttx/net/netstats.h>
#include "netdev/netdev.h"
#include "utils/utils.h"
#include "sixlowpan/sixlowpan.h"
#include "ipforward/ipforward.h"
#include "devif/devif.h"
#if defined(CONFIG_NET_IPFORWARD) && defined(CONFIG_NET_IPv4)
/****************************************************************************
* Private Functions
****************************************************************************/
/****************************************************************************
* Name: ipv4_hdrsize
*
* Description:
* Return the size of the IPv4 header and the following.
*
* Input Parameters:
* ipv4 - A pointer to the IPv4 header in within the IPv4 packet. This
* is immediately followed by the L3 header which may be TCP, UDP
* or ICMP.
*
* 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 ipv4_hdrsize(FAR struct ipv4_hdr_s *ipv4)
{
uint16_t iphdrlen;
/* Get the IP header length (accounting for possible options). */
iphdrlen = (ipv4->vhl & IPv4_HLMASK) << 2;
/* Size is also determined by the following protocol header, */
switch (ipv4->proto)
{
#ifdef CONFIG_NET_TCP
case IP_PROTO_TCP:
{
FAR struct tcp_hdr_s *tcp =
(FAR struct tcp_hdr_s *)((FAR uint8_t *)ipv4 + iphdrlen);
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 iphdrlen + tcpsize;
}
break;
#endif
#ifdef CONFIG_NET_UDP
case IP_PROTO_UDP:
return iphdrlen + UDP_HDRLEN;
break;
#endif
#ifdef CONFIG_NET_ICMP
case IP_PROTO_ICMP:
return iphdrlen + ICMP_HDRLEN;
break;
#endif
default:
nwarn("WARNING: Unrecognized proto: %u\n", ipv4->proto);
return -EPROTONOSUPPORT;
}
}
#endif
/****************************************************************************
* Name: ipv4_decr_ttl
*
* Description:
* Decrement the IPv4 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:
* ipv4 - A pointer to the IPv4 header in within the IPv4 packet to be
* forwarded.
*
* Returned Value:
* The new TTL value is returned. A value <= 0 means the hop limit has
* expired.
*
****************************************************************************/
static int ipv4_decr_ttl(FAR struct ipv4_hdr_s *ipv4)
{
uint16_t iphdrlen;
uint16_t sum;
int ttl;
/* Check time-to-live (TTL) */
ttl = (int)ipv4->ttl - 1;
if (ttl <= 0)
{
#ifdef CONFIG_NET_ICMP
/* Return an ICMP error packet back to the sender. */
# warning Missing logic
#endif
/* Return zero which must cause the packet to be dropped */
return 0;
}
/* Save the updated TTL value */
ipv4->ttl = ttl;
/* Get the IP header length (accounting for possible options). */
iphdrlen = (ipv4->vhl & IPv4_HLMASK) << 2;
/* Re-calculate the IPv4 checksum. This checksum is the Internet checksum
* of the 20 bytes of the IPv4 header. This checksum will be different
* because we just modify the IPv4 TTL.
*/
ipv4->ipchksum = 0;
sum = chksum(0, (FAR const uint8_t *)ipv4, iphdrlen);
if (sum == 0)
{
sum = 0xffff;
}
else
{
sum = HTONS(sum);
}
ipv4->ipchksum = ~sum;
return ttl;
}
/****************************************************************************
* Name: ipv4_dev_forward
*
* Description:
* This function is called from ipv4_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 IPv4 packet.
* fwdddev - The device on which the packet must be forwarded.
* ipv4 - A pointer to the IPv4 header in within the IPv4 packet
*
* 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 (ipv4_input()) should drop the packet.
*
****************************************************************************/
static int ipv4_dev_forward(FAR struct net_driver_s *dev,
FAR struct net_driver_s *fwddev,
FAR struct ipv4_hdr_s *ipv4)
{
FAR struct forward_s *fwd = NULL;
#ifdef CONFIG_DEBUG_NET_WARN
int hdrsize;
#endif
int ret;
/* 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_IPv6
fwd->f_domain = PF_INET; /* IPv4 address domain */
#endif
#ifdef CONFIG_DEBUG_NET_WARN
/* Get the size of the IPv4 + L3 header. */
hdrsize = ipv4_hdrsize(ipv4);
if (hdrsize < IPv4_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
/* Try to allocate the head of an IOB chain. If this fails, the
* packet will be dropped; we are not operating in a context
* where waiting for an IOB is a good idea
*/
fwd->f_iob = iob_tryalloc(false);
if (fwd->f_iob == NULL)
{
nwarn("WARNING: iob_tryalloc() failed\n");
ret = -ENOMEM;
goto errout_with_fwd;
}
/* Copy the L2/L3 headers plus any following payload into an IOB chain.
* iob_trycopin() will not wait, but will fail there are no available
* IOBs.
*
* REVISIT: Consider an alternative design that does not require data
* copying. This would require a pool of d_buf's that are managed by
* the network rather than the network device.
*/
ret = iob_trycopyin(fwd->f_iob, (FAR const uint8_t *)ipv4,
dev->d_len, 0, false);
if (ret < 0)
{
nwarn("WARNING: iob_trycopyin() failed: %d\n", ret);
goto errout_with_iobchain;
}
/* Decrement the TTL in the copy of the IPv4 header (retaining the
* original TTL in the source to handle the broadcast case). If the
* TLL decrements to zero, then do not forward the packet.
*/
ret = ipv4_decr_ttl((FAR struct ipv4_hdr_s *)fwd->f_iob->io_data);
if (ret < 1)
{
nwarn("WARNING: Hop limit exceeded... Dropping!\n");
ret = -EMULTIHOP;
goto errout_with_iobchain;
}
/* Then set up to forward the packet according to the protocol. */
ret = ipfwd_forward(fwd);
if (ret >= 0)
{
dev->d_len = 0;
return OK;
}
errout_with_iobchain:
if (fwd != NULL && fwd->f_iob != NULL)
{
iob_free_chain(fwd->f_iob);
}
errout_with_fwd:
if (fwd != NULL)
{
ipfwd_free(fwd);
}
errout:
return ret;
}
/****************************************************************************
* Name: ipv4_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 IPv4 packet.
* ipv4 - A convenience pointer to the IPv4 header in within the IPv4
* 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
int ipv4_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 ipv4_hdr_s *ipv4;
int ret;
DEBUGASSERT(fwddev != NULL && dev != NULL && dev->d_buf != NULL);
/* Check if we are forwarding on the same device that we received the
* packet from.
*/
if (fwddev != dev)
{
/* Recover the pointer to the IPv4 header in the receiving device's
* d_buf.
*/
ipv4 = (FAR struct ipv4_hdr_s *)&dev->d_buf[NET_LL_HDRLEN(dev)];
/* Send the packet asynchrously on the forwarding device. */
ret = ipv4_dev_forward(dev, fwddev, ipv4);
if (ret < 0)
{
nwarn("WARNING: ipv4_dev_forward failed: %d\n", ret);
return ret;
}
}
return OK;
}
#endif
/****************************************************************************
* Public Functions
****************************************************************************/
/****************************************************************************
* Name: ipv4_forward
*
* Description:
* This function is called from ipv4_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 IPv4
* networks served by various network devices.
*
* Input Parameters:
* dev - The device on which the packet was received and which contains
* the IPv4 packet.
* ipv4 - A convenience pointer to the IPv4 header in within the IPv4
* 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 ipv4_input.
* - ipv4 points to the IPv4 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 (ipv4_input()) should drop the packet.
*
****************************************************************************/
int ipv4_forward(FAR struct net_driver_s *dev, FAR struct ipv4_hdr_s *ipv4)
{
in_addr_t destipaddr;
in_addr_t srcipaddr;
FAR struct net_driver_s *fwddev;
int ret;
/* Search for a device that can forward this packet. */
destipaddr = net_ip4addr_conv32(ipv4->destipaddr);
srcipaddr = net_ip4addr_conv32(ipv4->srcipaddr);
fwddev = netdev_findby_ripv4addr(srcipaddr, destipaddr);
if (fwddev == NULL)
{
nwarn("WARNING: Not routable\n");
return (ssize_t)-ENETUNREACH;
}
/* 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 = ipv4_dev_forward(dev, fwddev, ipv4);
if (ret < 0)
{
nwarn("WARNING: ipv4_dev_forward failed: %d\n", ret);
goto drop;
}
}
else
{
/* 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.
*/
#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 IPv4 address.
* This will involve ICMP.
*/
/* Correct dev->d_buf by adding back the L1 header length */
#endif
nwarn("WARNING: Packet forwarding to same device not supportedN\n");
ret = -ENOSYS;
goto drop;
}
/* Return success. ipv4_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:
ipv4_dropstats(ipv4);
dev->d_len = 0;
return ret;
}
/****************************************************************************
* Name: ipv4_forward_broadcast
*
* Description:
* This function is called from ipv4_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 IPv4 packet.
* ipv4 - A convenience pointer to the IPv4 header in within the IPv4
* 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 ipv4_input.
* - ipv4 points to the IPv4 header with dev->d_buf.
*
* Returned Value:
* None
*
****************************************************************************/
#ifdef CONFIG_NET_IPFORWARD_BROADCAST
void ipv4_forward_broadcast(FAR struct net_driver_s *dev,
FAR struct ipv4_hdr_s *ipv4)
{
/* Don't bother if the TTL would expire */
if (ipv4->ttl > 1)
{
/* Forward the the broadcast/multicast packet to all devices except,
* of course, the device that received the packet.
*/
netdev_foreach(ipv4_forward_callback, dev);
}
}
#endif
#endif /* CONFIG_NET_IPFORWARD && CONFIG_NET_IPv4 */
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