a8d3286258
Signed-off-by: chao an <anchao@xiaomi.com>
543 lines
16 KiB
C
543 lines
16 KiB
C
/****************************************************************************
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* net/ipforward/ipv4_forward.c
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*
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* Licensed to the Apache Software Foundation (ASF) under one or more
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* contributor license agreements. See the NOTICE file distributed with
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* this work for additional information regarding copyright ownership. The
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* ASF licenses this file to you under the Apache License, Version 2.0 (the
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* "License"); you may not use this file except in compliance with the
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* License. You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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* License for the specific language governing permissions and limitations
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* under the License.
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*
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****************************************************************************/
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/****************************************************************************
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* Included Files
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****************************************************************************/
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#include <nuttx/config.h>
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#include <string.h>
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#include <assert.h>
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#include <debug.h>
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#include <errno.h>
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#include <nuttx/mm/iob.h>
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#include <nuttx/net/net.h>
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#include <nuttx/net/netdev.h>
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#include <nuttx/net/netstats.h>
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#include "netdev/netdev.h"
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#include "utils/utils.h"
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#include "sixlowpan/sixlowpan.h"
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#include "ipforward/ipforward.h"
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#include "devif/devif.h"
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#if defined(CONFIG_NET_IPFORWARD) && defined(CONFIG_NET_IPv4)
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/****************************************************************************
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* Private Functions
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****************************************************************************/
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/****************************************************************************
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* Name: ipv4_hdrsize
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*
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* Description:
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* Return the size of the IPv4 header and the following.
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*
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* Input Parameters:
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* ipv4 - A pointer to the IPv4 header in within the IPv4 packet. This
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* is immediately followed by the L3 header which may be TCP, UDP
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* or ICMP.
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*
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* Returned Value:
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* The size of the combined L2 + L3 headers is returned on success. An
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* error is returned only if the prototype is not supported.
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*
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****************************************************************************/
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#ifdef CONFIG_DEBUG_NET_WARN
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static int ipv4_hdrsize(FAR struct ipv4_hdr_s *ipv4)
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{
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uint16_t iphdrlen;
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/* Get the IP header length (accounting for possible options). */
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iphdrlen = (ipv4->vhl & IPv4_HLMASK) << 2;
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/* Size is also determined by the following protocol header, */
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switch (ipv4->proto)
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{
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#ifdef CONFIG_NET_TCP
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case IP_PROTO_TCP:
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{
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FAR struct tcp_hdr_s *tcp =
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(FAR struct tcp_hdr_s *)((FAR uint8_t *)ipv4 + iphdrlen);
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unsigned int tcpsize;
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/* The TCP header length is encoded in the top 4 bits of the
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* tcpoffset field (in units of 32-bit words).
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*/
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tcpsize = ((uint16_t)tcp->tcpoffset >> 4) << 2;
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return iphdrlen + tcpsize;
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}
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break;
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#endif
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#ifdef CONFIG_NET_UDP
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case IP_PROTO_UDP:
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return iphdrlen + UDP_HDRLEN;
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break;
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#endif
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#ifdef CONFIG_NET_ICMP
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case IP_PROTO_ICMP:
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return iphdrlen + ICMP_HDRLEN;
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break;
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#endif
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default:
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nwarn("WARNING: Unrecognized proto: %u\n", ipv4->proto);
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return -EPROTONOSUPPORT;
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}
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}
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#endif
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/****************************************************************************
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* Name: ipv4_decr_ttl
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*
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* Description:
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* Decrement the IPv4 TTL (time to live value). TTL field is set by the
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* sender of the packet and reduced by every router on the route to its
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* destination. If the TTL field reaches zero before the datagram arrives
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* at its destination, then the datagram is discarded and an ICMP error
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* packet (11 - Time Exceeded) is sent back to the sender.
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*
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* The purpose of the TTL field is to avoid a situation in which an
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* undeliverable datagram keeps circulating on an Internet system, and
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* such a system eventually becoming swamped by such "immortals".
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*
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* Input Parameters:
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* ipv4 - A pointer to the IPv4 header in within the IPv4 packet to be
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* forwarded.
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*
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* Returned Value:
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* The new TTL value is returned. A value <= 0 means the hop limit has
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* expired.
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*
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****************************************************************************/
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static int ipv4_decr_ttl(FAR struct ipv4_hdr_s *ipv4)
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{
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uint16_t iphdrlen;
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uint16_t sum;
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int ttl;
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/* Check time-to-live (TTL) */
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ttl = (int)ipv4->ttl - 1;
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if (ttl <= 0)
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{
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#ifdef CONFIG_NET_ICMP
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/* Return an ICMP error packet back to the sender. */
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# warning Missing logic
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#endif
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/* Return zero which must cause the packet to be dropped */
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return 0;
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}
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/* Save the updated TTL value */
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ipv4->ttl = ttl;
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/* Get the IP header length (accounting for possible options). */
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iphdrlen = (ipv4->vhl & IPv4_HLMASK) << 2;
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/* Re-calculate the IPv4 checksum. This checksum is the Internet checksum
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* of the 20 bytes of the IPv4 header. This checksum will be different
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* because we just modify the IPv4 TTL.
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*/
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ipv4->ipchksum = 0;
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sum = chksum(0, (FAR const uint8_t *)ipv4, iphdrlen);
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if (sum == 0)
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{
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sum = 0xffff;
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}
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else
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{
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sum = HTONS(sum);
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}
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ipv4->ipchksum = ~sum;
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return ttl;
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}
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/****************************************************************************
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* Name: ipv4_dev_forward
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*
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* Description:
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* This function is called from ipv4_forward when it is necessary to
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* forward a packet from the current device to different device. In this
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* case, the forwarding operation must be performed asynchronously when
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* the TX poll is received from the forwarding device.
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*
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* Input Parameters:
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* dev - The device on which the packet was received and which
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* contains the IPv4 packet.
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* fwdddev - The device on which the packet must be forwarded.
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* ipv4 - A pointer to the IPv4 header in within the IPv4 packet
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*
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* Returned Value:
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* Zero is returned if the packet was successfully forward; A negated
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* errno value is returned if the packet is not forwardable. In that
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* latter case, the caller (ipv4_input()) should drop the packet.
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*
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****************************************************************************/
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static int ipv4_dev_forward(FAR struct net_driver_s *dev,
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FAR struct net_driver_s *fwddev,
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FAR struct ipv4_hdr_s *ipv4)
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{
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FAR struct forward_s *fwd = NULL;
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#ifdef CONFIG_DEBUG_NET_WARN
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int hdrsize;
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#endif
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int ret;
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/* Verify that the full packet will fit within the forwarding devices MTU.
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* We provide no support for fragmenting forwarded packets.
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*/
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if (NET_LL_HDRLEN(fwddev) + dev->d_len > NETDEV_PKTSIZE(fwddev))
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{
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nwarn("WARNING: Packet > MTU... Dropping\n");
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ret = -EFBIG;
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goto errout;
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}
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/* Get a pre-allocated forwarding structure, This structure will be
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* completely zeroed when we receive it.
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*/
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fwd = ipfwd_alloc();
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if (fwd == NULL)
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{
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nwarn("WARNING: Failed to allocate forwarding structure\n");
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ret = -ENOMEM;
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goto errout;
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}
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/* Initialize the easy stuff in the forwarding structure */
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fwd->f_dev = fwddev; /* Forwarding device */
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#ifdef CONFIG_NET_IPv6
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fwd->f_domain = PF_INET; /* IPv4 address domain */
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#endif
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#ifdef CONFIG_DEBUG_NET_WARN
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/* Get the size of the IPv4 + L3 header. */
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hdrsize = ipv4_hdrsize(ipv4);
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if (hdrsize < IPv4_HDRLEN)
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{
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nwarn("WARNING: Could not determine L2+L3 header size\n");
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ret = -EPROTONOSUPPORT;
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goto errout_with_fwd;
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}
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/* The L2/L3 headers must fit within one, contiguous IOB. */
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if (hdrsize > CONFIG_IOB_BUFSIZE)
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{
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nwarn("WARNING: Header is too big for pre-allocated structure\n");
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ret = -E2BIG;
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goto errout_with_fwd;
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}
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#endif
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/* Try to allocate the head of an IOB chain. If this fails, the
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* packet will be dropped; we are not operating in a context
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* where waiting for an IOB is a good idea
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*/
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fwd->f_iob = iob_tryalloc(false);
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if (fwd->f_iob == NULL)
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{
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nwarn("WARNING: iob_tryalloc() failed\n");
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ret = -ENOMEM;
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goto errout_with_fwd;
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}
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/* Copy the L2/L3 headers plus any following payload into an IOB chain.
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* iob_trycopin() will not wait, but will fail there are no available
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* IOBs.
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*
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* REVISIT: Consider an alternative design that does not require data
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* copying. This would require a pool of d_buf's that are managed by
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* the network rather than the network device.
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*/
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ret = iob_trycopyin(fwd->f_iob, (FAR const uint8_t *)ipv4,
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dev->d_len, 0, false);
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if (ret < 0)
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{
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nwarn("WARNING: iob_trycopyin() failed: %d\n", ret);
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goto errout_with_iobchain;
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}
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/* Decrement the TTL in the copy of the IPv4 header (retaining the
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* original TTL in the source to handle the broadcast case). If the
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* TLL decrements to zero, then do not forward the packet.
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*/
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ret = ipv4_decr_ttl((FAR struct ipv4_hdr_s *)fwd->f_iob->io_data);
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if (ret < 1)
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{
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nwarn("WARNING: Hop limit exceeded... Dropping!\n");
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ret = -EMULTIHOP;
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goto errout_with_iobchain;
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}
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/* Then set up to forward the packet according to the protocol. */
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ret = ipfwd_forward(fwd);
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if (ret >= 0)
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{
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dev->d_len = 0;
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return OK;
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}
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errout_with_iobchain:
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if (fwd != NULL && fwd->f_iob != NULL)
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{
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iob_free_chain(fwd->f_iob);
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}
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errout_with_fwd:
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if (fwd != NULL)
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{
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ipfwd_free(fwd);
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}
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errout:
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return ret;
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}
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/****************************************************************************
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* Name: ipv4_forward_callback
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*
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* Description:
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* This function is a callback from netdev_foreach. It implements the
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* the broadcast forwarding action for each network device (other than, of
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* course, the device that received the packet).
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*
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* Input Parameters:
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* dev - The device on which the packet was received and which contains
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* the IPv4 packet.
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* ipv4 - A convenience pointer to the IPv4 header in within the IPv4
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* packet
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*
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* Returned Value:
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* Typically returns zero (meaning to continue the enumeration), but will
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* return a non-zero to stop the enumeration if an error occurs.
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*
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****************************************************************************/
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#ifdef CONFIG_NET_IPFORWARD_BROADCAST
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int ipv4_forward_callback(FAR struct net_driver_s *fwddev, FAR void *arg)
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{
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FAR struct net_driver_s *dev = (FAR struct net_driver_s *)arg;
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FAR struct ipv4_hdr_s *ipv4;
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int ret;
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DEBUGASSERT(fwddev != NULL && dev != NULL && dev->d_buf != NULL);
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/* Check if we are forwarding on the same device that we received the
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* packet from.
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*/
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if (fwddev != dev)
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{
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/* Recover the pointer to the IPv4 header in the receiving device's
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* d_buf.
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*/
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ipv4 = IPv4BUF;
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/* Send the packet asynchrously on the forwarding device. */
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ret = ipv4_dev_forward(dev, fwddev, ipv4);
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if (ret < 0)
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{
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nwarn("WARNING: ipv4_dev_forward failed: %d\n", ret);
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return ret;
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}
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}
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return OK;
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}
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#endif
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/****************************************************************************
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* Public Functions
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****************************************************************************/
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/****************************************************************************
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* Name: ipv4_forward
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*
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* Description:
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* This function is called from ipv4_input when a packet is received that
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* is not destined for us. In this case, the packet may need to be
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* forwarded to another device (or sent back out the same device)
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* depending configuration, routing table information, and the IPv4
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* networks served by various network devices.
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*
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* Input Parameters:
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* dev - The device on which the packet was received and which contains
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* the IPv4 packet.
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* ipv4 - A convenience pointer to the IPv4 header in within the IPv4
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* packet
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*
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* On input:
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* - dev->d_buf holds the received packet.
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* - dev->d_len holds the length of the received packet MINUS the
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* size of the L1 header. That was subtracted out by ipv4_input.
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* - ipv4 points to the IPv4 header with dev->d_buf.
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*
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* Returned Value:
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* Zero is returned if the packet was successfully forward; A negated
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* errno value is returned if the packet is not forwardable. In that
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* latter case, the caller (ipv4_input()) should drop the packet.
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*
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****************************************************************************/
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int ipv4_forward(FAR struct net_driver_s *dev, FAR struct ipv4_hdr_s *ipv4)
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{
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in_addr_t destipaddr;
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in_addr_t srcipaddr;
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FAR struct net_driver_s *fwddev;
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int ret;
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/* Search for a device that can forward this packet. */
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destipaddr = net_ip4addr_conv32(ipv4->destipaddr);
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srcipaddr = net_ip4addr_conv32(ipv4->srcipaddr);
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fwddev = netdev_findby_ripv4addr(srcipaddr, destipaddr);
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if (fwddev == NULL)
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{
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nwarn("WARNING: Not routable\n");
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return (ssize_t)-ENETUNREACH;
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}
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/* Check if we are forwarding on the same device that we received the
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* packet from.
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*/
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if (fwddev != dev)
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{
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/* Send the packet asynchrously on the forwarding device. */
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ret = ipv4_dev_forward(dev, fwddev, ipv4);
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if (ret < 0)
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{
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nwarn("WARNING: ipv4_dev_forward failed: %d\n", ret);
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goto drop;
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}
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}
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else
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{
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/* Single network device. The use case here is where an endpoint acts
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* as a hub in a star configuration. This is typical for a wireless
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* star configuration where not all endpoints are accessible from all
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* other endpoints, but seems less useful for a wired network.
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*/
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#ifdef CONFIG_NET_ETHERNET
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/* REVISIT: For Ethernet we may have to fix up the Ethernet header:
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* - source MAC, the MAC of the current device.
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* - dest MAC, the MAC associated with the destination IPv4 address.
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* This will involve ICMP.
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*/
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/* Correct dev->d_buf by adding back the L1 header length */
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#endif
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nwarn("WARNING: Packet forwarding to same device not supportedN\n");
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ret = -ENOSYS;
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goto drop;
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}
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/* Return success. ipv4_input will return to the network driver with
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* dev->d_len set to the packet size and the network driver will perform
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* the transfer.
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*/
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return OK;
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drop:
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ipv4_dropstats(ipv4);
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dev->d_len = 0;
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return ret;
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}
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/****************************************************************************
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* Name: ipv4_forward_broadcast
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*
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* Description:
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* This function is called from ipv4_input when a broadcast or multicast
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* packet is received. If CONFIG_NET_IPFORWARD_BROADCAST is enabled, this
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* function will forward the broadcast packet to other networks through
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* other network devices.
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*
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* Input Parameters:
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* dev - The device on which the packet was received and which contains
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* the IPv4 packet.
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* ipv4 - A convenience pointer to the IPv4 header in within the IPv4
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* packet
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*
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* On input:
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* - dev->d_buf holds the received packet.
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* - dev->d_len holds the length of the received packet MINUS the
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* size of the L1 header. That was subtracted out by ipv4_input.
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* - ipv4 points to the IPv4 header with dev->d_buf.
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*
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* Returned Value:
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* None
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*
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****************************************************************************/
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#ifdef CONFIG_NET_IPFORWARD_BROADCAST
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void ipv4_forward_broadcast(FAR struct net_driver_s *dev,
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FAR struct ipv4_hdr_s *ipv4)
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{
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/* Don't bother if the TTL would expire */
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if (ipv4->ttl > 1)
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{
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/* Forward the the broadcast/multicast packet to all devices except,
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* of course, the device that received the packet.
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*/
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netdev_foreach(ipv4_forward_callback, dev);
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}
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}
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#endif
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#endif /* CONFIG_NET_IPFORWARD && CONFIG_NET_IPv4 */
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