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Just use raw sockets for listening to DHCP requests. A UDP SO_BROADCAST

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socket was previously used only for receiving RENEWING packets, and it
added needless complexity and was somewhat fragile.
This commit is contained in:
Nicholas J. Kain
2014-04-16 01:00:36 -04:00
parent ca85a6ba9f
commit 07cbd88049
7 changed files with 31 additions and 102 deletions
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2
src/arp.c
View File

@@ -447,7 +447,7 @@ void arp_success(struct client_state_t *cs)
cs->routerAddr = get_option_router(&garp.dhcp_packet);
arp_get_gw_hwaddr(cs);
}
set_listen_none(cs);
stop_dhcp_listen(cs);
write_leasefile(temp_addr);
arp_announcement(cs);
if (client_config.quit_after_lease)

83
src/dhcp.c
View File

@@ -48,12 +48,6 @@
#include "options.h"
#include "sockd.h"
typedef enum {
LM_NONE = 0,
LM_COOKED,
LM_RAW
} listen_mode_t;
static int get_udp_unicast_socket(struct client_state_t *cs)
{
char buf[32];
@@ -67,11 +61,6 @@ static int get_raw_broadcast_socket(void)
return request_sockd_fd("s", 1, NULL);
}
static int get_udp_listen_socket(void)
{
return request_sockd_fd("U", 1, NULL);
}
static int get_raw_listen_socket(struct client_state_t *cs)
{
char resp;
@@ -85,8 +74,8 @@ static int get_raw_listen_socket(struct client_state_t *cs)
return fd;
}
// Broadcast a DHCP message using a UDP socket.
static ssize_t send_dhcp_cooked(struct client_state_t *cs,
// Unicast a DHCP message using a UDP socket.
static ssize_t send_dhcp_unicast(struct client_state_t *cs,
struct dhcpmsg *payload)
{
ssize_t ret = -1;
@@ -127,23 +116,6 @@ static ssize_t send_dhcp_cooked(struct client_state_t *cs,
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 client_state_t *cs,
struct dhcpmsg *packet)
{
memset(packet, 0, sizeof *packet);
ssize_t bytes = safe_read(cs->listenFd, (char *)packet, sizeof *packet);
if (bytes < 0) {
if (errno == EAGAIN || errno == EWOULDBLOCK)
return -2;
log_warning("%s: (%s) read error %s", client_config.interface,
__func__, 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
@@ -352,39 +324,24 @@ static ssize_t send_dhcp_raw(struct dhcpmsg *payload)
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)
void start_dhcp_listen(struct client_state_t *cs)
{
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(); break;
}
if (cs->listenFd >= 0)
return;
cs->listenFd = get_raw_listen_socket(cs);
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)
void stop_dhcp_listen(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);
if (cs->listenFd < 0)
return;
epoll_del(cs->epollFd, cs->listenFd);
close(cs->listenFd);
cs->listenFd = -1;
}
static int validate_dhcp_packet(struct client_state_t *cs, size_t len,
@@ -436,19 +393,17 @@ static int validate_dhcp_packet(struct client_state_t *cs, size_t len,
void handle_packet(struct client_state_t *cs)
{
if (cs->listenFd < 0)
return;
struct dhcpmsg packet;
ssize_t r;
switch (cs->listenMode) {
case LM_RAW: r = get_raw_packet(cs, &packet); break;
case LM_COOKED: r = get_cooked_packet(cs, &packet); break;
default: return;
}
ssize_t r = get_raw_packet(cs, &packet);
if (r < 0) {
// Not a transient issue handled by packet collection functions.
if (r != -2) {
log_error("%s: Error reading from listening socket: %s. Reopening.",
client_config.interface, strerror(errno));
change_listen_mode(cs, cs->listenMode);
stop_dhcp_listen(cs);
start_dhcp_listen(cs);
}
return;
}
@@ -515,7 +470,7 @@ ssize_t send_renew(struct client_state_t *cs)
add_option_vendor(&packet);
add_option_hostname(&packet);
log_line("%s: Sending a renew request...", client_config.interface);
return send_dhcp_cooked(cs, &packet);
return send_dhcp_unicast(cs, &packet);
}
ssize_t send_rebind(struct client_state_t *cs)
@@ -548,6 +503,6 @@ ssize_t send_release(struct client_state_t *cs)
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);
return send_dhcp_unicast(cs, &packet);
}

5
src/dhcp.h
View File

@@ -81,9 +81,8 @@ struct udp_dhcp_packet {
struct dhcpmsg data;
};
void set_listen_raw(struct client_state_t *cs);
void set_listen_cooked(struct client_state_t *cs);
void set_listen_none(struct client_state_t *cs);
void start_dhcp_listen(struct client_state_t *cs);
void stop_dhcp_listen(struct client_state_t *cs);
void handle_packet(struct client_state_t *cs);
ssize_t send_discover(struct client_state_t *cs);
ssize_t send_selecting(struct client_state_t *cs);

2
src/ndhc.c
View File

@@ -295,7 +295,7 @@ static void do_ndhc_work(void)
epoll_add(cs.epollFd, ifchSock[0]);
epoll_add(cs.epollFd, ifchStream[0]);
epoll_add(cs.epollFd, sockdStream[0]);
set_listen_raw(&cs);
start_dhcp_listen(&cs);
nowts = curms();
goto jumpstart;

1
src/ndhc.h
View File

@@ -40,7 +40,6 @@ struct client_state_t {
int ifsPrevState;
int ifchWorking; // ifch is performing interface changes.
int ifDeconfig; // Set if the interface has already been deconfigured.
int listenMode;
int epollFd, signalFd, listenFd, arpFd, nlFd;
int nlPortId;
uint32_t clientAddr, serverAddr, routerAddr;

28
src/sockd.c
View File

@@ -245,30 +245,6 @@ out:
return -1;
}
// Returns fd of new listen socket bound to 0.0.0.0:@68 on interface @inf
// on success, or -1 on failure.
static int create_udp_listen_socket(void)
{
int fd = create_udp_socket(INADDR_ANY, DHCP_CLIENT_PORT,
client_config.interface);
if (fd < 0)
return -1;
int opt = 1;
if (setsockopt(fd, SOL_SOCKET, SO_BROADCAST, &opt, sizeof opt) < 0) {
log_error("%s: (%s) Set broadcast failed: %s",
client_config.interface, __func__, strerror(errno));
close(fd);
return -1;
}
return fd;
}
static int create_udp_send_socket(uint32_t client_addr)
{
return create_udp_socket(client_addr, DHCP_CLIENT_PORT,
client_config.interface);
}
static int create_raw_listen_socket(bool *using_bpf)
{
static const struct sock_filter sf_dhcp[] = {
@@ -478,7 +454,6 @@ static size_t execute_sockd(char *buf, size_t buflen)
xfer_fd(fd, using_bpf ? 'L' : 'l');
return 1;
}
case 'U': xfer_fd(create_udp_listen_socket(), 'U'); return 1;
case 'a': {
bool using_bpf;
int fd = create_arp_basic_socket(&using_bpf);
@@ -505,7 +480,8 @@ static size_t execute_sockd(char *buf, size_t buflen)
suicide("%s: (%s) 'u' does not have necessary arguments: %zu",
client_config.interface, __func__, buflen);
memcpy(&client_addr, buf + 1, sizeof client_addr);
xfer_fd(create_udp_send_socket(client_addr), 'u');
xfer_fd(create_udp_socket(client_addr, DHCP_CLIENT_PORT,
client_config.interface), 'u');
return 5;
}
default: suicide("%s: (%s) received invalid commands: '%c'",

10
src/state.c
View File

@@ -106,7 +106,7 @@ void reinit_selecting(struct client_state_t *cs, int timeout)
reinit_shared_deconfig(cs);
cs->dhcpState = DS_SELECTING;
dhcp_wake_ts = curms() + timeout;
set_listen_raw(cs);
start_dhcp_listen(cs);
}
static void set_released(struct client_state_t *cs)
@@ -114,7 +114,7 @@ static void set_released(struct client_state_t *cs)
reinit_shared_deconfig(cs);
cs->dhcpState = DS_RELEASED;
dhcp_wake_ts = -1;
set_listen_none(cs);
stop_dhcp_listen(cs);
}
// Triggered after a DHCP lease request packet has been sent and no reply has
@@ -143,7 +143,7 @@ static void bound_timeout(struct client_state_t *cs, long long nowts)
return;
}
cs->dhcpState = DS_RENEWING;
set_listen_cooked(cs);
start_dhcp_listen(cs);
renewing_timeout(cs, nowts);
}
@@ -267,7 +267,7 @@ static void an_packet(struct client_state_t *cs, struct dhcpmsg *packet,
client_config.interface, cs->lease);
cs->dhcpState = DS_BOUND;
arp_set_defense_mode(cs);
set_listen_none(cs);
stop_dhcp_listen(cs);
}
} else if (msgtype == DHCPNAK) {
@@ -358,7 +358,7 @@ static void frenew(struct client_state_t *cs)
if (cs->dhcpState == DS_BOUND) {
log_line("%s: Forcing a DHCP renew...", client_config.interface);
cs->dhcpState = DS_RENEWING;
set_listen_cooked(cs);
start_dhcp_listen(cs);
if (send_renew(cs) < 0)
log_warning("%s: Failed to send a renew request packet.",
client_config.interface);