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sd-dhcp: use FIONREAD to get correct size of incoming DHCP packet

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This avoids the problem of broken DHCP servers sending us too big packets that don't fit in our buffer.
This commit is contained in:
Tom Gundersen 2014-02-23 17:30:13 +01:00
parent 3bb621e1e6
commit 5266a81ea2
2 changed files with 26 additions and 12 deletions
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2
src/libsystemd-dhcp/dhcp-packet.c
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@ -119,6 +119,8 @@ void dhcp_packet_append_ip_headers(DHCPPacket *packet, uint16_t len) {
int dhcp_packet_verify_headers(DHCPPacket *packet, size_t len) {
size_t hdrlen;
assert(packet);
/* IP */
if (len < DHCP_IP_SIZE) {

36
src/libsystemd-dhcp/sd-dhcp-client.c
View file

@ -23,6 +23,7 @@
#include <stdio.h>
#include <net/ethernet.h>
#include <sys/param.h>
#include <sys/ioctl.h>
#include "util.h"
#include "list.h"
@ -847,16 +848,23 @@ error:
static int client_receive_message_udp(sd_event_source *s, int fd,
uint32_t revents, void *userdata) {
sd_dhcp_client *client = userdata;
uint8_t buf[sizeof(DHCPMessage) + DHCP_MIN_OPTIONS_SIZE];
int buflen = sizeof(buf);
int len, r = 0;
_cleanup_free_ DHCPMessage *message = NULL;
int buflen = 0, len, r;
usec_t time_now;
assert(s);
assert(client);
assert(client->event);
len = read(fd, &buf, buflen);
r = ioctl(fd, FIONREAD, &buflen);
if (r < 0 || buflen <= 0)
buflen = sizeof(DHCPMessage) + DHCP_MIN_OPTIONS_SIZE;
message = malloc0(buflen);
if (!message)
return -ENOMEM;
len = read(fd, message, buflen);
if (len < 0)
return 0;
@ -864,29 +872,33 @@ static int client_receive_message_udp(sd_event_source *s, int fd,
if (r < 0)
return client_stop(client, r);
return client_handle_message(client, (DHCPMessage *) buf, len,
return client_handle_message(client, message, len,
time_now);
}
static int client_receive_message_raw(sd_event_source *s, int fd,
uint32_t revents, void *userdata) {
sd_dhcp_client *client = userdata;
uint8_t buf[sizeof(DHCPPacket) + DHCP_MIN_OPTIONS_SIZE];
int buflen = sizeof(buf);
int len, r = 0;
DHCPPacket *packet;
_cleanup_free_ DHCPPacket *packet = NULL;
int buflen = 0, len, r;
usec_t time_now;
assert(s);
assert(client);
assert(client->event);
len = read(fd, &buf, buflen);
r = ioctl(fd, FIONREAD, &buflen);
if (r < 0 || buflen <= 0)
buflen = sizeof(DHCPPacket) + DHCP_MIN_OPTIONS_SIZE;
packet = malloc0(buflen);
if (!packet)
return -ENOMEM;
len = read(fd, packet, buflen);
if (len < 0)
return 0;
packet = (DHCPPacket *) buf;
r = dhcp_packet_verify_headers(packet, len);
if (r < 0)
return 0;