u-boot/net/ping.c
David Rivshin 51723c5581 net: Do not respond to ICMP_ECHO_REQUEST if we do not have an IP address
While doing DHCP the interface IP is set to 0.0.0.0. This causes the
check in net.c on dst_ip to be effectively skipped, and all IP datagrams
are accepted up the IP stack. In the case of an ICMP_ECHO_REQUEST for the
matching MAC address (regardless of destination IP), the result is that
an ICMP_ECHO_REPLY is sent. The source address of the ICMP_ECHO_REPLY is
0.0.0.0, which is an illegal source address.

This can happen in common practice with the following sequence:
DHCP (U-Boot or OS) acquires IP address 10.0.0.1
System reboots
U-Boot starts DHCP and send DHCP DISCOVER
DHCP server decides to OFFER 10.0.0.1 again
  (perhaps because of existing lease or manual configuration)
DHCP server tries to PING 10.0.0.1 to see if anyone is squatting on it
DHCP server still has our MAC address in its ARP table for 10.0.0.1
U-Boot receives PING, and responds with an illegal source address
This may further result in a the DHCP server seeing the response as
  confirmation that someone is squatting on 10.0.0.1, and picking a
  new IP address from the pool to try again

Signed-off-by: David Rivshin <drivshin@allworx.com>
2021-01-19 09:15:02 -05:00

119 lines
2.8 KiB
C

// SPDX-License-Identifier: GPL-2.0
/*
* Copied from Linux Monitor (LiMon) - Networking.
*
* Copyright 1994 - 2000 Neil Russell.
* (See License)
* Copyright 2000 Roland Borde
* Copyright 2000 Paolo Scaffardi
* Copyright 2000-2002 Wolfgang Denk, wd@denx.de
*/
#include "ping.h"
#include "arp.h"
#include <log.h>
#include <net.h>
static ushort ping_seq_number;
/* The ip address to ping */
struct in_addr net_ping_ip;
static void set_icmp_header(uchar *pkt, struct in_addr dest)
{
/*
* Construct an IP and ICMP header.
*/
struct icmp_hdr *icmp = (struct icmp_hdr *)(pkt + IP_HDR_SIZE);
net_set_ip_header(pkt, dest, net_ip, IP_ICMP_HDR_SIZE, IPPROTO_ICMP);
icmp->type = ICMP_ECHO_REQUEST;
icmp->code = 0;
icmp->checksum = 0;
icmp->un.echo.id = 0;
icmp->un.echo.sequence = htons(ping_seq_number++);
icmp->checksum = compute_ip_checksum(icmp, ICMP_HDR_SIZE);
}
static int ping_send(void)
{
uchar *pkt;
int eth_hdr_size;
/* XXX always send arp request */
debug_cond(DEBUG_DEV_PKT, "sending ARP for %pI4\n", &net_ping_ip);
net_arp_wait_packet_ip = net_ping_ip;
eth_hdr_size = net_set_ether(net_tx_packet, net_null_ethaddr, PROT_IP);
pkt = (uchar *)net_tx_packet + eth_hdr_size;
set_icmp_header(pkt, net_ping_ip);
/* size of the waiting packet */
arp_wait_tx_packet_size = eth_hdr_size + IP_ICMP_HDR_SIZE;
/* and do the ARP request */
arp_wait_try = 1;
arp_wait_timer_start = get_timer(0);
arp_request();
return 1; /* waiting */
}
static void ping_timeout_handler(void)
{
eth_halt();
net_set_state(NETLOOP_FAIL); /* we did not get the reply */
}
void ping_start(void)
{
printf("Using %s device\n", eth_get_name());
net_set_timeout_handler(10000UL, ping_timeout_handler);
ping_send();
}
void ping_receive(struct ethernet_hdr *et, struct ip_udp_hdr *ip, int len)
{
struct icmp_hdr *icmph = (struct icmp_hdr *)&ip->udp_src;
struct in_addr src_ip;
int eth_hdr_size;
uchar *tx_packet;
switch (icmph->type) {
case ICMP_ECHO_REPLY:
src_ip = net_read_ip((void *)&ip->ip_src);
if (src_ip.s_addr == net_ping_ip.s_addr)
net_set_state(NETLOOP_SUCCESS);
return;
case ICMP_ECHO_REQUEST:
if (net_ip.s_addr == 0)
return;
eth_hdr_size = net_update_ether(et, et->et_src, PROT_IP);
debug_cond(DEBUG_DEV_PKT,
"Got ICMP ECHO REQUEST, return %d bytes\n",
eth_hdr_size + len);
ip->ip_sum = 0;
ip->ip_off = 0;
net_copy_ip((void *)&ip->ip_dst, &ip->ip_src);
net_copy_ip((void *)&ip->ip_src, &net_ip);
ip->ip_sum = compute_ip_checksum(ip, IP_HDR_SIZE);
icmph->type = ICMP_ECHO_REPLY;
icmph->checksum = 0;
icmph->checksum = compute_ip_checksum(icmph, len - IP_HDR_SIZE);
tx_packet = net_get_async_tx_pkt_buf();
memcpy(tx_packet, et, eth_hdr_size + len);
net_send_packet(tx_packet, eth_hdr_size + len);
return;
/* default:
return;*/
}
}