Just use raw sockets for listening to DHCP requests. A UDP SO_BROADCAST
socket was previously used only for receiving RENEWING packets, and it added needless complexity and was somewhat fragile.
This commit is contained in:
85
src/dhcp.c
85
src/dhcp.c
@ -48,12 +48,6 @@
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#include "options.h"
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#include "sockd.h"
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typedef enum {
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LM_NONE = 0,
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LM_COOKED,
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LM_RAW
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} listen_mode_t;
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static int get_udp_unicast_socket(struct client_state_t *cs)
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{
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char buf[32];
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@ -67,11 +61,6 @@ static int get_raw_broadcast_socket(void)
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return request_sockd_fd("s", 1, NULL);
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}
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static int get_udp_listen_socket(void)
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{
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return request_sockd_fd("U", 1, NULL);
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}
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static int get_raw_listen_socket(struct client_state_t *cs)
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{
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char resp;
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@ -85,9 +74,9 @@ static int get_raw_listen_socket(struct client_state_t *cs)
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return fd;
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}
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// Broadcast a DHCP message using a UDP socket.
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static ssize_t send_dhcp_cooked(struct client_state_t *cs,
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struct dhcpmsg *payload)
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// Unicast a DHCP message using a UDP socket.
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static ssize_t send_dhcp_unicast(struct client_state_t *cs,
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struct dhcpmsg *payload)
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{
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ssize_t ret = -1;
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int fd = get_udp_unicast_socket(cs);
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@ -127,23 +116,6 @@ static ssize_t send_dhcp_cooked(struct client_state_t *cs,
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return ret;
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}
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// Read a packet from a cooked socket. Returns -1 on fatal error, -2 on
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// transient error.
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static ssize_t get_cooked_packet(struct client_state_t *cs,
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struct dhcpmsg *packet)
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{
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memset(packet, 0, sizeof *packet);
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ssize_t bytes = safe_read(cs->listenFd, (char *)packet, sizeof *packet);
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if (bytes < 0) {
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if (errno == EAGAIN || errno == EWOULDBLOCK)
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return -2;
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log_warning("%s: (%s) read error %s", client_config.interface,
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__func__, strerror(errno));
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return -1;
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}
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return bytes;
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}
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// When summing ones-complement 16-bit values using a 32-bit unsigned
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// representation, fold the carry bits that have spilled into the upper
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// 16-bits of the 32-bit unsigned value back into the 16-bit ones-complement
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@ -352,39 +324,24 @@ static ssize_t send_dhcp_raw(struct dhcpmsg *payload)
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return ret;
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}
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// Switch listen socket between raw (if-bound), kernel (ip-bound), and none
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static void change_listen_mode(struct client_state_t *cs, int new_mode)
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void start_dhcp_listen(struct client_state_t *cs)
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{
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cs->listenMode = new_mode;
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if (cs->listenFd >= 0) {
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epoll_del(cs->epollFd, cs->listenFd);
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close(cs->listenFd);
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cs->listenFd = -1;
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}
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switch (cs->listenMode) {
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default: return;
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case LM_RAW: cs->listenFd = get_raw_listen_socket(cs); break;
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case LM_COOKED: cs->listenFd = get_udp_listen_socket(); break;
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}
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if (cs->listenFd >= 0)
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return;
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cs->listenFd = get_raw_listen_socket(cs);
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if (cs->listenFd < 0)
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suicide("%s: FATAL: Couldn't listen on socket: %s",
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client_config.interface, strerror(errno));
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epoll_add(cs->epollFd, cs->listenFd);
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}
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void set_listen_raw(struct client_state_t *cs)
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void stop_dhcp_listen(struct client_state_t *cs)
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{
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change_listen_mode(cs, LM_RAW);
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}
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void set_listen_cooked(struct client_state_t *cs)
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{
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change_listen_mode(cs, LM_COOKED);
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}
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void set_listen_none(struct client_state_t *cs)
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{
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change_listen_mode(cs, LM_NONE);
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if (cs->listenFd < 0)
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return;
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epoll_del(cs->epollFd, cs->listenFd);
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close(cs->listenFd);
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cs->listenFd = -1;
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}
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static int validate_dhcp_packet(struct client_state_t *cs, size_t len,
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@ -436,19 +393,17 @@ static int validate_dhcp_packet(struct client_state_t *cs, size_t len,
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void handle_packet(struct client_state_t *cs)
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{
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if (cs->listenFd < 0)
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return;
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struct dhcpmsg packet;
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ssize_t r;
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switch (cs->listenMode) {
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case LM_RAW: r = get_raw_packet(cs, &packet); break;
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case LM_COOKED: r = get_cooked_packet(cs, &packet); break;
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default: return;
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}
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ssize_t r = get_raw_packet(cs, &packet);
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if (r < 0) {
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// Not a transient issue handled by packet collection functions.
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if (r != -2) {
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log_error("%s: Error reading from listening socket: %s. Reopening.",
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client_config.interface, strerror(errno));
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change_listen_mode(cs, cs->listenMode);
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stop_dhcp_listen(cs);
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start_dhcp_listen(cs);
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}
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return;
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}
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@ -515,7 +470,7 @@ ssize_t send_renew(struct client_state_t *cs)
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add_option_vendor(&packet);
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add_option_hostname(&packet);
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log_line("%s: Sending a renew request...", client_config.interface);
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return send_dhcp_cooked(cs, &packet);
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return send_dhcp_unicast(cs, &packet);
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}
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ssize_t send_rebind(struct client_state_t *cs)
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@ -548,6 +503,6 @@ ssize_t send_release(struct client_state_t *cs)
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add_option_reqip(&packet, cs->clientAddr);
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add_option_serverid(&packet, cs->serverAddr);
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log_line("%s: Sending a release message...", client_config.interface);
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return send_dhcp_cooked(cs, &packet);
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return send_dhcp_unicast(cs, &packet);
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}
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