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Move source from ndhc/ to src/ since ifchd is no longer a separate program.

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This commit is contained in:
Nicholas J. Kain
2014-04-06 16:57:06 -04:00
parent b511d45c2f
commit b761889025
37 changed files with 8 additions and 8 deletions
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src/dhcp.c Normal file
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/* dhcp.c - general DHCP protocol handling
*
* Copyright (c) 2004-2014 Nicholas J. Kain <njkain at gmail dot com>
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* - Redistributions of source code must retain the above copyright notice,
* this list of conditions and the following disclaimer.
*
* - Redistributions in binary form must reproduce the above copyright notice,
* this list of conditions and the following disclaimer in the documentation
* and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*/
#include <stdlib.h>
#include <stddef.h>
#include <stdio.h>
#include <unistd.h>
#include <string.h>
#include <arpa/inet.h>
#include <sys/types.h>
#include <netpacket/packet.h>
#include <net/ethernet.h>
#include <errno.h>
#include "nk/log.h"
#include "nk/io.h"
#include "nk/random.h"
#include "dhcp.h"
#include "state.h"
#include "arp.h"
#include "ifchange.h"
#include "sys.h"
#include "options.h"
#include "sockd.h"
typedef enum {
LM_NONE = 0,
LM_COOKED,
LM_RAW
} listen_mode_t;
static int get_udp_unicast_socket(void)
{
return request_sockd_fd("u", 1, NULL);
}
static int get_raw_broadcast_socket(void)
{
return request_sockd_fd("s", 1, NULL);
}
static int get_udp_listen_socket(struct client_state_t *cs)
{
char buf[32];
buf[0] = 'u';
memcpy(buf + 1, &cs->clientAddr, sizeof cs->clientAddr);
return request_sockd_fd(buf, 1 + sizeof cs->clientAddr, NULL);
}
static int get_raw_listen_socket(struct client_state_t *cs)
{
char resp;
int fd = request_sockd_fd("L", 1, &resp);
switch (resp) {
case 'L': cs->using_dhcp_bpf = 1; break;
case 'l': cs->using_dhcp_bpf = 0; break;
default: suicide("%s: (%s) expected l or L sockd reply but got %c",
client_config.interface, __func__, resp);
}
return fd;
}
// Broadcast a DHCP message using a UDP socket.
static ssize_t send_dhcp_cooked(struct client_state_t *cs,
struct dhcpmsg *payload)
{
ssize_t ret = -1;
int fd = get_udp_unicast_socket();
if (fd < 0)
goto out;
struct sockaddr_in raddr = {
.sin_family = AF_INET,
.sin_port = htons(DHCP_SERVER_PORT),
.sin_addr.s_addr = cs->serverAddr,
};
if (connect(fd, (struct sockaddr *)&raddr, sizeof(struct sockaddr)) < 0) {
log_error("%s: (%s) connect failed: %s", client_config.interface,
__func__, strerror(errno));
goto out_fd;
}
// Send packets that are as short as possible.
ssize_t endloc = get_end_option_idx(payload);
if (endloc < 0) {
log_error("%s: (%s) No end marker. Not sending.",
client_config.interface, __func__);
goto out_fd;
}
size_t payload_len =
sizeof *payload - (sizeof payload->options - 1 - endloc);
ret = safe_write(fd, (const char *)payload, payload_len);
if (ret < 0 || (size_t)ret != payload_len)
log_error("%s: (%s) write failed: %d", client_config.interface,
__func__, ret);
out_fd:
close(fd);
out:
return ret;
}
// Read a packet from a cooked socket. Returns -1 on fatal error, -2 on
// transient error.
static ssize_t get_cooked_packet(struct dhcpmsg *packet, int fd)
{
memset(packet, 0, sizeof *packet);
ssize_t bytes = safe_read(fd, (char *)packet, sizeof *packet);
if (bytes < 0) {
if (errno == EAGAIN || errno == EWOULDBLOCK)
return -2;
log_line("%s: Read on listen socket failed: %s",
client_config.interface, strerror(errno));
return -1;
}
return bytes;
}
// When summing ones-complement 16-bit values using a 32-bit unsigned
// representation, fold the carry bits that have spilled into the upper
// 16-bits of the 32-bit unsigned value back into the 16-bit ones-complement
// binary value.
static inline uint16_t foldcarry(uint32_t v)
{
v = (v >> 16) + (v & 0xffff);
v += v >> 16;
return v;
}
// This function is not suitable for summing buffers that are greater than
// 128k bytes in length: failure case will be incorrect checksums via
// unsigned overflow, which is a defined operation and is safe. This limit
// should not be an issue for IPv4 or IPv6 packet, which are limited to
// at most 64k bytes.
static uint16_t net_checksum(void *buf, size_t size)
{
uint32_t sum = 0;
int odd = size & 0x01;
size_t i;
size &= ~((size_t)0x01);
size >>= 1;
uint8_t *b = buf;
for (i = 0; i < size; ++i) {
uint16_t hi = b[i*2];
uint16_t lo = b[i*2+1];
sum += ntohs((lo + (hi << 8)));
}
if (odd) {
uint16_t hi = b[i*2];
uint16_t lo = 0;
sum += ntohs((lo + (hi << 8)));
}
return ~foldcarry(sum);
}
// For two sequences of bytes A and B that return checksums CS(A) and CS(B),
// this function will calculate the checksum CS(AB) of the concatenated value
// AB given the checksums of the individual parts CS(A) and CS(B).
static inline uint16_t net_checksum_add(uint16_t a, uint16_t b)
{
return ~foldcarry((~a & 0xffff) + (~b & 0xffff));
}
// Returns 1 if IP checksum is correct, otherwise 0.
static int ip_checksum(struct ip_udp_dhcp_packet *packet)
{
return net_checksum(&packet->ip, sizeof packet->ip) == 0;
}
// Returns 1 if UDP checksum is correct, otherwise 0.
static int udp_checksum(struct ip_udp_dhcp_packet *packet)
{
struct iphdr ph = {
.saddr = packet->ip.saddr,
.daddr = packet->ip.daddr,
.protocol = packet->ip.protocol,
.tot_len = packet->udp.len,
};
uint16_t udpcs = net_checksum(&packet->udp, ntohs(packet->udp.len));
uint16_t hdrcs = net_checksum(&ph, sizeof ph);
uint16_t cs = net_checksum_add(udpcs, hdrcs);
return cs == 0;
}
static int get_raw_packet_validate_bpf(struct ip_udp_dhcp_packet *packet)
{
if (packet->ip.version != IPVERSION) {
log_warning("%s: IP version is not IPv4.", client_config.interface);
return 0;
}
if (packet->ip.ihl != sizeof packet->ip >> 2) {
log_warning("%s: IP header length incorrect.",
client_config.interface);
return 0;
}
if (packet->ip.protocol != IPPROTO_UDP) {
log_warning("%s: IP header is not UDP: %d",
client_config.interface, packet->ip.protocol);
return 0;
}
if (ntohs(packet->udp.dest) != DHCP_CLIENT_PORT) {
log_warning("%s: UDP destination port incorrect: %d",
client_config.interface, ntohs(packet->udp.dest));
return 0;
}
if (ntohs(packet->udp.len) !=
ntohs(packet->ip.tot_len) - sizeof packet->ip) {
log_warning("%s: UDP header length incorrect.",
client_config.interface);
return 0;
}
return 1;
}
// Read a packet from a raw socket. Returns -1 on fatal error, -2 on
// transient error.
static ssize_t get_raw_packet(struct client_state_t *cs,
struct dhcpmsg *payload)
{
struct ip_udp_dhcp_packet packet;
memset(&packet, 0, sizeof packet);
ssize_t inc = safe_read(cs->listenFd, (char *)&packet, sizeof packet);
if (inc < 0) {
if (errno == EAGAIN || errno == EWOULDBLOCK)
return -2;
log_warning("%s: (%s) read error %s", client_config.interface,
__func__, strerror(errno));
return -1;
}
if (inc != ntohs(packet.ip.tot_len)) {
log_warning("%s: UDP length does not match header length fields.",
client_config.interface);
return -2;
}
if (!cs->using_dhcp_bpf && !get_raw_packet_validate_bpf(&packet))
return -2;
if (!ip_checksum(&packet)) {
log_warning("%s: IP header checksum incorrect.",
client_config.interface);
return -2;
}
if (packet.udp.check && !udp_checksum(&packet)) {
log_error("%s: Packet with bad UDP checksum received. Ignoring.",
client_config.interface);
return -2;
}
size_t l = ntohs(packet.ip.tot_len) - sizeof packet.ip - sizeof packet.udp;
memcpy(payload, &packet.data, l);
return l;
}
// Broadcast a DHCP message using a raw socket.
static ssize_t send_dhcp_raw(struct dhcpmsg *payload)
{
ssize_t ret = -1;
int fd = get_raw_broadcast_socket();
if (fd < 0)
return ret;
// Send packets that are as short as possible.
ssize_t endloc = get_end_option_idx(payload);
if (endloc < 0) {
log_error("%s: (%s) No end marker. Not sending.",
client_config.interface, __func__);
close(fd);
return ret;
}
size_t padding = sizeof payload->options - 1 - endloc;
size_t iud_len = sizeof(struct ip_udp_dhcp_packet) - padding;
size_t ud_len = sizeof(struct udp_dhcp_packet) - padding;
struct iphdr ph = {
.saddr = INADDR_ANY,
.daddr = INADDR_BROADCAST,
.protocol = IPPROTO_UDP,
.tot_len = htons(ud_len),
};
struct ip_udp_dhcp_packet iudmsg = {
.ip = {
.saddr = INADDR_ANY,
.daddr = INADDR_BROADCAST,
.protocol = IPPROTO_UDP,
.tot_len = htons(iud_len),
.ihl = sizeof iudmsg.ip >> 2,
.version = IPVERSION,
.ttl = IPDEFTTL,
},
.data = *payload,
};
iudmsg.udp.source = htons(DHCP_CLIENT_PORT);
iudmsg.udp.dest = htons(DHCP_SERVER_PORT);
iudmsg.udp.len = htons(ud_len);
iudmsg.udp.check = 0;
uint16_t udpcs = net_checksum(&iudmsg.udp, ud_len);
uint16_t phcs = net_checksum(&ph, sizeof ph);
iudmsg.udp.check = net_checksum_add(udpcs, phcs);
iudmsg.ip.check = net_checksum(&iudmsg.ip, sizeof iudmsg.ip);
struct sockaddr_ll da = {
.sll_family = AF_PACKET,
.sll_protocol = htons(ETH_P_IP),
.sll_pkttype = PACKET_BROADCAST,
.sll_ifindex = client_config.ifindex,
.sll_halen = 6,
};
memcpy(da.sll_addr, "\xff\xff\xff\xff\xff\xff", 6);
ret = safe_sendto(fd, (const char *)&iudmsg, iud_len, 0,
(struct sockaddr *)&da, sizeof da);
if (ret < 0)
log_error("%s: (%s) sendto failed: %s", client_config.interface,
__func__, strerror(errno));
close(fd);
return ret;
}
// Switch listen socket between raw (if-bound), kernel (ip-bound), and none
static void change_listen_mode(struct client_state_t *cs, int new_mode)
{
cs->listenMode = new_mode;
if (cs->listenFd >= 0) {
epoll_del(cs->epollFd, cs->listenFd);
close(cs->listenFd);
cs->listenFd = -1;
}
switch (cs->listenMode) {
default: return;
case LM_RAW: cs->listenFd = get_raw_listen_socket(cs); break;
case LM_COOKED: cs->listenFd = get_udp_listen_socket(cs); break;
}
if (cs->listenFd < 0)
suicide("%s: FATAL: Couldn't listen on socket: %s",
client_config.interface, strerror(errno));
epoll_add(cs->epollFd, cs->listenFd);
}
void set_listen_raw(struct client_state_t *cs)
{
change_listen_mode(cs, LM_RAW);
}
void set_listen_cooked(struct client_state_t *cs)
{
change_listen_mode(cs, LM_COOKED);
}
void set_listen_none(struct client_state_t *cs)
{
change_listen_mode(cs, LM_NONE);
}
static int validate_dhcp_packet(struct client_state_t *cs, size_t len,
struct dhcpmsg *packet, uint8_t *msgtype)
{
if (len < offsetof(struct dhcpmsg, options)) {
log_warning("%s: Packet is too short to contain magic cookie. Ignoring.",
client_config.interface);
return 0;
}
if (ntohl(packet->cookie) != DHCP_MAGIC) {
log_warning("%s: Packet with bad magic number. Ignoring.",
client_config.interface);
return 0;
}
if (packet->xid != cs->xid) {
log_warning("%s: Packet XID %lx does not equal our XID %lx. Ignoring.",
client_config.interface, packet->xid, cs->xid);
return 0;
}
if (memcmp(packet->chaddr, client_config.arp, sizeof client_config.arp)) {
log_warning("%s: Packet client MAC %2.2x:%2.2x:%2.2x:%2.2x:%2.2x:%2.2x does not equal our MAC %2.2x:%2.2x:%2.2x:%2.2x:%2.2x:%2.2x. Ignoring it.",
client_config.interface,
packet->chaddr[0], packet->chaddr[1], packet->chaddr[2],
packet->chaddr[3], packet->chaddr[4], packet->chaddr[5],
client_config.arp[0], client_config.arp[1],
client_config.arp[2], client_config.arp[3],
client_config.arp[4], client_config.arp[5]);
return 0;
}
*msgtype = get_option_msgtype(packet);
if (!*msgtype) {
log_warning("%s: Packet does not specify a DHCP message type. Ignoring.",
client_config.interface);
return 0;
}
char clientid[MAX_DOPT_SIZE];
size_t cidlen = get_option_clientid(packet, clientid, MAX_DOPT_SIZE);
if (cidlen == 0)
return 1;
if (memcmp(client_config.clientid, clientid,
min_size_t(cidlen, client_config.clientid_len))) {
log_warning("%s: Packet clientid does not match our clientid. Ignoring.",
client_config.interface);
return 0;
}
return 1;
}
void handle_packet(struct client_state_t *cs)
{
uint8_t msgtype;
struct dhcpmsg packet;
if (cs->listenMode == LM_NONE)
return;
ssize_t r = cs->listenMode == LM_RAW ?
get_raw_packet(cs, &packet) : get_cooked_packet(&packet, cs->listenFd);
if (r < 0) {
// Transient issue handled by packet collection functions.
if (r == -2 || (r == -1 && errno == EINTR))
return;
log_error("%s: Error reading from listening socket: %s. Reopening.",
client_config.interface, strerror(errno));
change_listen_mode(cs, cs->listenMode);
return;
}
size_t len = (size_t)r;
if (!validate_dhcp_packet(cs, len, &packet, &msgtype))
return;
packet_action(cs, &packet, msgtype);
}
// Initialize a DHCP client packet that will be sent to a server
static struct dhcpmsg init_packet(char type, uint32_t xid)
{
struct dhcpmsg packet = {
.op = 1, // BOOTREQUEST (client)
.htype = 1, // ETH_10MB
.hlen = 6, // ETH_10MB_LEN
.cookie = htonl(DHCP_MAGIC),
.options[0] = DCODE_END,
.xid = xid,
};
add_option_msgtype(&packet, type);
memcpy(packet.chaddr, client_config.arp, 6);
add_option_clientid(&packet, client_config.clientid,
client_config.clientid_len);
return packet;
}
ssize_t send_discover(struct client_state_t *cs)
{
struct dhcpmsg packet = init_packet(DHCPDISCOVER, cs->xid);
if (cs->clientAddr)
add_option_reqip(&packet, cs->clientAddr);
add_option_maxsize(&packet);
add_option_request_list(&packet);
add_option_vendor(&packet);
add_option_hostname(&packet);
log_line("%s: Discovering DHCP servers...", client_config.interface);
return send_dhcp_raw(&packet);
}
ssize_t send_selecting(struct client_state_t *cs)
{
char clibuf[INET_ADDRSTRLEN];
struct dhcpmsg packet = init_packet(DHCPREQUEST, cs->xid);
add_option_reqip(&packet, cs->clientAddr);
add_option_serverid(&packet, cs->serverAddr);
add_option_maxsize(&packet);
add_option_request_list(&packet);
add_option_vendor(&packet);
add_option_hostname(&packet);
inet_ntop(AF_INET, &(struct in_addr){.s_addr = cs->clientAddr},
clibuf, sizeof clibuf);
log_line("%s: Sending a selection request for %s...",
client_config.interface, clibuf);
return send_dhcp_raw(&packet);
}
ssize_t send_renew(struct client_state_t *cs)
{
struct dhcpmsg packet = init_packet(DHCPREQUEST, cs->xid);
packet.ciaddr = cs->clientAddr;
add_option_maxsize(&packet);
add_option_request_list(&packet);
add_option_vendor(&packet);
add_option_hostname(&packet);
log_line("%s: Sending a renew request...", client_config.interface);
return send_dhcp_cooked(cs, &packet);
}
ssize_t send_rebind(struct client_state_t *cs)
{
struct dhcpmsg packet = init_packet(DHCPREQUEST, cs->xid);
packet.ciaddr = cs->clientAddr;
add_option_reqip(&packet, cs->clientAddr);
add_option_maxsize(&packet);
add_option_request_list(&packet);
add_option_vendor(&packet);
add_option_hostname(&packet);
log_line("%s: Sending a rebind request...", client_config.interface);
return send_dhcp_raw(&packet);
}
ssize_t send_decline(struct client_state_t *cs, uint32_t server)
{
struct dhcpmsg packet = init_packet(DHCPDECLINE, cs->xid);
add_option_reqip(&packet, cs->clientAddr);
add_option_serverid(&packet, server);
log_line("%s: Sending a decline message...", client_config.interface);
return send_dhcp_raw(&packet);
}
ssize_t send_release(struct client_state_t *cs)
{
struct dhcpmsg packet = init_packet(DHCPRELEASE,
nk_random_u32(&cs->rnd32_state));
packet.ciaddr = cs->clientAddr;
add_option_reqip(&packet, cs->clientAddr);
add_option_serverid(&packet, cs->serverAddr);
log_line("%s: Sending a release message...", client_config.interface);
return send_dhcp_cooked(cs, &packet);
}