+static int client_receive_message_udp(sd_event_source *s, int fd,
+ uint32_t revents, void *userdata) {
+ sd_dhcp_client *client = userdata;
+ _cleanup_free_ DHCPMessage *message = NULL;
+ int buflen = 0, len, r;
+ usec_t time_now;
+
+ assert(s);
+ assert(client);
+ assert(client->event);
+
+ 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;
+
+ r = sd_event_get_now_monotonic(client->event, &time_now);
+ if (r < 0)
+ return client_stop(client, r);
+
+ 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;
+ _cleanup_free_ DHCPPacket *packet = NULL;
+ usec_t time_now;
+ uint8_t cmsgbuf[CMSG_LEN(sizeof(struct tpacket_auxdata))];
+ struct iovec iov = {};
+ struct msghdr msg = {
+ .msg_iov = &iov,
+ .msg_iovlen = 1,
+ .msg_control = cmsgbuf,
+ .msg_controllen = sizeof(cmsgbuf),
+ };
+ struct cmsghdr *cmsg;
+ bool checksum = true;
+ int buflen = 0, len, r;
+
+ assert(s);
+ assert(client);
+ assert(client->event);
+
+ r = ioctl(fd, FIONREAD, &buflen);
+ if (r < 0 || buflen <= 0)
+ buflen = sizeof(DHCPPacket) + DHCP_MIN_OPTIONS_SIZE;
+
+ packet = malloc0(buflen);
+ if (!packet)
+ return -ENOMEM;
+
+ iov.iov_base = packet;
+ iov.iov_len = buflen;
+
+ len = recvmsg(fd, &msg, 0);
+ if (len < 0) {
+ log_dhcp_client(client, "could not receive message from raw "
+ "socket: %s", strerror(errno));
+ return 0;
+ }
+
+ for (cmsg = CMSG_FIRSTHDR(&msg); cmsg; cmsg = CMSG_NXTHDR(&msg, cmsg)) {
+ if (cmsg->cmsg_level == SOL_PACKET && cmsg->cmsg_type == PACKET_AUXDATA) {
+ struct tpacket_auxdata *aux = (void *)CMSG_DATA(cmsg);
+
+ checksum = !(aux->tp_status & TP_STATUS_CSUMNOTREADY);
+ break;
+ }
+ }
+
+ r = dhcp_packet_verify_headers(packet, len, checksum);
+ if (r < 0)
+ return 0;
+
+ len -= DHCP_IP_UDP_SIZE;
+
+ r = sd_event_get_now_monotonic(client->event, &time_now);
+ if (r < 0)
+ return client_stop(client, r);
+
+ return client_handle_message(client, &packet->dhcp, len, time_now);
+}
+