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dhcp: Handle received DHCP Offer message

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Create a function for handling the full IP, UDP and DHCP packet
and tie it to the main loop. Verify IP and UDP headers and checksum.
Creat a new lease structure with using the values supplied in the
DHCP message. Free the lease structure when client is stopped.

Split out socket handling into a creation and a sending part. As a
result modify the test code.
This commit is contained in:
Patrik Flykt 2013-12-09 23:43:26 +02:00 committed by Zbigniew Jędrzejewski-Szmek
parent d3d8ac2f2b
commit 8c00042c93
5 changed files with 252 additions and 22 deletions
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195
src/libsystemd-dhcp/dhcp-client.c
View file

@ -32,17 +32,31 @@
#define DHCP_CLIENT_MIN_OPTIONS_SIZE 312
struct DHCPLease {
uint32_t lifetime;
uint32_t address;
uint32_t server_address;
uint32_t subnet_mask;
uint32_t router;
};
typedef struct DHCPLease DHCPLease;
struct sd_dhcp_client {
DHCPState state;
sd_event *event;
sd_event_source *timeout_resend;
int index;
int fd;
union sockaddr_union link;
sd_event_source *receive_message;
uint8_t *req_opts;
size_t req_opts_size;
uint32_t last_addr;
struct ether_addr mac_addr;
uint32_t xid;
usec_t start_time;
DHCPLease *lease;
};
static const uint8_t default_req_opts[] = {
@ -128,6 +142,13 @@ static int client_stop(sd_dhcp_client *client, int error)
assert_return(client->state != DHCP_STATE_INIT &&
client->state != DHCP_STATE_INIT_REBOOT, -EALREADY);
client->receive_message =
sd_event_source_unref(client->receive_message);
if (client->fd >= 0)
close(client->fd);
client->fd = -1;
client->timeout_resend = sd_event_source_unref(client->timeout_resend);
switch (client->state) {
@ -135,6 +156,7 @@ static int client_stop(sd_dhcp_client *client, int error)
case DHCP_STATE_INIT:
case DHCP_STATE_SELECTING:
client->start_time = 0;
client->state = DHCP_STATE_INIT;
break;
@ -148,6 +170,11 @@ static int client_stop(sd_dhcp_client *client, int error)
break;
}
if (client->lease) {
free(client->lease);
client->lease = NULL;
}
return 0;
}
@ -278,9 +305,10 @@ static int client_send_discover(sd_dhcp_client *client, uint16_t secs)
discover->ip.check = client_checksum(&discover->ip,
sizeof(discover->ip));
err = dhcp_network_send_raw_packet(client->index, discover, len);
err = dhcp_network_send_raw_socket(client->fd, &client->link,
discover, len);
return 0;
return err;
}
static int client_timeout_resend(sd_event_source *s, uint64_t usec,
@ -334,6 +362,154 @@ error:
return 0;
}
static int client_parse_offer(uint8_t code, uint8_t len, const uint8_t *option,
void *user_data)
{
DHCPLease *lease = user_data;
be32_t val;
switch(code) {
case DHCP_OPTION_IP_ADDRESS_LEASE_TIME:
if (len == 4) {
memcpy(&val, option, 4);
lease->lifetime = be32toh(val);
}
break;
case DHCP_OPTION_SERVER_IDENTIFIER:
if (len >= 4)
memcpy(&lease->server_address, option, 4);
break;
case DHCP_OPTION_SUBNET_MASK:
if (len >= 4)
memcpy(&lease->subnet_mask, option, 4);
break;
case DHCP_OPTION_ROUTER:
if (len >= 4)
memcpy(&lease->router, option, 4);
break;
}
return 0;
}
static int client_receive_offer(sd_dhcp_client *client, DHCPPacket *offer,
size_t len)
{
size_t hdrlen;
DHCPLease *lease;
if (len < (DHCP_IP_UDP_SIZE + DHCP_MESSAGE_SIZE))
return -EINVAL;
hdrlen = offer->ip.ihl * 4;
if (hdrlen < 20 || hdrlen > len || client_checksum(&offer->ip,
hdrlen))
return -EINVAL;
offer->ip.check = offer->udp.len;
offer->ip.ttl = 0;
if (hdrlen + be16toh(offer->udp.len) > len ||
client_checksum(&offer->ip.ttl, be16toh(offer->udp.len) + 12))
return -EINVAL;
if (be16toh(offer->udp.source) != DHCP_PORT_SERVER ||
be16toh(offer->udp.dest) != DHCP_PORT_CLIENT)
return -EINVAL;
if (offer->dhcp.op != BOOTREPLY)
return -EINVAL;
if (be32toh(offer->dhcp.xid) != client->xid)
return -EINVAL;
if (memcmp(&offer->dhcp.chaddr[0], &client->mac_addr.ether_addr_octet,
ETHER_ADDR_LEN))
return -EINVAL;
lease = new0(DHCPLease, 1);
if (!lease)
return -ENOMEM;
len = len - DHCP_IP_UDP_SIZE;
if (dhcp_option_parse(&offer->dhcp, len, client_parse_offer,
lease) != DHCP_OFFER)
goto error;
lease->address = offer->dhcp.yiaddr;
if (lease->address == INADDR_ANY ||
lease->server_address == INADDR_ANY ||
lease->subnet_mask == INADDR_ANY ||
lease->lifetime == 0)
goto error;
client->lease = lease;
return 0;
error:
free(lease);
return -ENOMSG;
}
static int client_receive_raw_message(sd_event_source *s, int fd,
uint32_t revents, void *userdata)
{
sd_dhcp_client *client = userdata;
uint8_t buf[sizeof(DHCPPacket) + DHCP_CLIENT_MIN_OPTIONS_SIZE];
int buflen = sizeof(buf);
int len;
DHCPPacket *message;
len = read(fd, &buf, buflen);
if (len < 0)
goto error;
message = (DHCPPacket *)&buf;
switch (client->state) {
case DHCP_STATE_SELECTING:
if (client_receive_offer(client, message, len) >= 0) {
client->receive_message =
sd_event_source_unref(client->receive_message);
close(client->fd);
client->fd = -1;
client->timeout_resend =
sd_event_source_unref(client->timeout_resend);
client->state = DHCP_STATE_REQUESTING;
}
break;
case DHCP_STATE_INIT:
case DHCP_STATE_INIT_REBOOT:
case DHCP_STATE_REBOOTING:
case DHCP_STATE_REQUESTING:
case DHCP_STATE_BOUND:
case DHCP_STATE_RENEWING:
case DHCP_STATE_REBINDING:
break;
}
error:
return 0;
}
int sd_dhcp_client_start(sd_dhcp_client *client)
{
int err;
@ -345,6 +521,20 @@ int sd_dhcp_client_start(sd_dhcp_client *client)
client->xid = random_u();
client->fd = dhcp_network_bind_raw_socket(client->index,
&client->link);
if (client->fd < 0) {
err = client->fd;
goto error;
}
err = sd_event_add_io(client->event, client->fd, EPOLLIN,
client_receive_raw_message, client,
&client->receive_message);
if (err < 0)
goto error;
err = sd_event_add_monotonic(client->event, now(CLOCK_MONOTONIC), 0,
client_timeout_resend, client,
&client->timeout_resend);
@ -377,6 +567,7 @@ sd_dhcp_client *sd_dhcp_client_new(sd_event *event)
client->event = sd_event_ref(event);
client->state = DHCP_STATE_INIT;
client->index = -1;
client->fd = -1;
client->req_opts_size = ELEMENTSOF(default_req_opts);

7
src/libsystemd-dhcp/dhcp-internal.h
View file

@ -22,10 +22,15 @@
***/
#include <stdint.h>
#include <linux/if_packet.h>
#include "socket-util.h"
#include "dhcp-protocol.h"
int dhcp_network_send_raw_packet(int index, const void *packet, size_t len);
int dhcp_network_bind_raw_socket(int index, union sockaddr_union *link);
int dhcp_network_send_raw_socket(int s, const union sockaddr_union *link,
const void *packet, size_t len);
int dhcp_option_append(uint8_t **buf, size_t *buflen, uint8_t code,
size_t optlen, const void *optval);

40
src/libsystemd-dhcp/dhcp-network.c
View file

@ -30,26 +30,36 @@
#include "dhcp-internal.h"
int dhcp_network_send_raw_packet(int index, const void *packet, size_t len)
{
_cleanup_close_ int s;
union sockaddr_union link = {};
int dhcp_network_bind_raw_socket(int index, union sockaddr_union *link)
{
int s;
s = socket(AF_PACKET, SOCK_DGRAM | SOCK_CLOEXEC, htons(ETH_P_IP));
s = socket(AF_PACKET, SOCK_DGRAM | SOCK_CLOEXEC | SOCK_NONBLOCK,
htons(ETH_P_IP));
if (s < 0)
return -errno;
link.ll.sll_family = AF_PACKET;
link.ll.sll_protocol = htons(ETH_P_IP);
link.ll.sll_ifindex = index;
link.ll.sll_halen = ETH_ALEN;
memset(&link.ll.sll_addr, 0xff, ETH_ALEN);
link->ll.sll_family = AF_PACKET;
link->ll.sll_protocol = htons(ETH_P_IP);
link->ll.sll_ifindex = index;
link->ll.sll_halen = ETH_ALEN;
memset(link->ll.sll_addr, 0xff, ETH_ALEN);
if (bind(s, &link.sa, sizeof(link.ll)) < 0)
if (bind(s, &link->sa, sizeof(link->ll)) < 0) {
close(s);
return -errno;
}
if (sendto(s, packet, len, 0, &link.sa, sizeof(link.ll)) < 0)
return -errno;
return 0;
return s;
}
int dhcp_network_send_raw_socket(int s, const union sockaddr_union *link,
const void *packet, size_t len)
{
int err = 0;
if (sendto(s, packet, len, 0, &link->sa, sizeof(link->ll)) < 0)
err = -errno;
return err;
}

6
src/libsystemd-dhcp/dhcp-protocol.h
View file

@ -55,6 +55,10 @@ struct DHCPPacket {
typedef struct DHCPPacket DHCPPacket;
#define DHCP_IP_SIZE (int32_t)(sizeof(struct iphdr))
#define DHCP_IP_UDP_SIZE (int32_t)(sizeof(struct udphdr) + DHCP_IP_SIZE)
#define DHCP_MESSAGE_SIZE (int32_t)(sizeof(DHCPMessage))
enum {
DHCP_PORT_SERVER = 67,
DHCP_PORT_CLIENT = 68,
@ -102,8 +106,10 @@ enum {
DHCP_OPTION_DOMAIN_NAME = 15,
DHCP_OPTION_NTP_SERVER = 42,
DHCP_OPTION_REQUESTED_IP_ADDRESS = 50,
DHCP_OPTION_IP_ADDRESS_LEASE_TIME = 51,
DHCP_OPTION_OVERLOAD = 52,
DHCP_OPTION_MESSAGE_TYPE = 53,
DHCP_OPTION_SERVER_IDENTIFIER = 54,
DHCP_OPTION_PARAMETER_REQUEST_LIST = 55,
DHCP_OPTION_CLIENT_IDENTIFIER = 61,
DHCP_OPTION_END = 255,

26
src/libsystemd-dhcp/test-dhcp-client.c
View file

@ -23,8 +23,12 @@
#include <assert.h>
#include <errno.h>
#include <stdio.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <unistd.h>
#include "util.h"
#include "socket-util.h"
#include "dhcp-protocol.h"
#include "dhcp-internal.h"
@ -34,6 +38,8 @@ static struct ether_addr mac_addr = {
.ether_addr_octet = {'A', 'B', 'C', '1', '2', '3'}
};
static int test_fd[2];
static void test_request_basic(sd_event *e)
{
sd_dhcp_client *client;
@ -125,14 +131,15 @@ static int check_options(uint8_t code, uint8_t len, const uint8_t *option,
return 0;
}
int dhcp_network_send_raw_packet(int index, const void *packet, size_t len)
int dhcp_network_send_raw_socket(int s, const union sockaddr_union *link,
const void *packet, size_t len)
{
size_t size;
_cleanup_free_ DHCPPacket *discover;
uint16_t ip_check, udp_check;
int res;
assert(index == 42);
assert(s >= 0);
assert(packet);
size = sizeof(DHCPPacket) + 4;
@ -146,8 +153,8 @@ int dhcp_network_send_raw_packet(int index, const void *packet, size_t len)
assert(discover->ip.protocol == IPPROTO_UDP);
assert(discover->ip.saddr == INADDR_ANY);
assert(discover->ip.daddr == INADDR_BROADCAST);
assert(discover->udp.source == ntohs(DHCP_PORT_CLIENT));
assert(discover->udp.dest == ntohs(DHCP_PORT_SERVER));
assert(discover->udp.source == be16toh(DHCP_PORT_CLIENT));
assert(discover->udp.dest == be16toh(DHCP_PORT_SERVER));
ip_check = discover->ip.check;
@ -172,6 +179,14 @@ int dhcp_network_send_raw_packet(int index, const void *packet, size_t len)
return 575;
}
int dhcp_network_bind_raw_socket(int index, union sockaddr_union *link)
{
if (socketpair(AF_UNIX, SOCK_STREAM, 0, test_fd) < 0)
return -errno;
return test_fd[0];
}
static void test_discover_message(sd_event *e)
{
sd_dhcp_client *client;
@ -188,6 +203,9 @@ static void test_discover_message(sd_event *e)
res = sd_dhcp_client_start(client);
assert(res == 0 || res == -EINPROGRESS);
close(test_fd[0]);
close(test_fd[1]);
}
int main(int argc, char *argv[])