packet.c

#include "packet.h"
#include "logger.h"
#include "netsock.h"

#include <endian.h>
#include <assert.h>
#include <errno.h>

extern const struct in6_addr in6addr_localmcast;

#define copy_buf_to_var_inc(buf, type, var)             \
  do {                                                  \
    type* tmp = &(var);                                 \
    memcpy(tmp, (buf), sizeof(type));                   \
    buf = (__typeof__ (buf))((char*)(buf) + sizeof(type));  \
  } while(0);

#define copy_var_to_buf_inc(buf, type, var)             \
  do {                                                  \
    type* tmp = &(var);                                 \
    memcpy((buf), tmp, sizeof(type));                   \
    buf = (__typeof__ (buf))((char*)(buf) + sizeof(type));  \
  } while(0);

ssize_t _packet_size(uint8_t command, ssize_t payload_count) {
  ssize_t len = 0;

  switch (command) {
  case DDHCP_MSG_UPDATECLAIM:
    len = 16 + payload_count * 7;
    break;

  case DDHCP_MSG_INQUIRE:
    len = 16 + payload_count * 4;
    break;

  case DDHCP_MSG_LEASEACK:
  case DDHCP_MSG_LEASENAK:
  case DDHCP_MSG_RENEWLEASE:
    len = 16 + sizeof(struct ddhcp_renew_payload);

    break;

  default:
    WARNING("_packet_size(...): Unknown command: %i/%li\n", command, payload_count);
    return -1;
    break;
  }

  if (len == 0) {
    ERROR("_packet_size(%i,%li): calculated zero length!", command, payload_count);
  }

  return len;
}

ATTR_NONNULL_ALL struct ddhcp_mcast_packet* new_ddhcp_packet(uint8_t command, ddhcp_config* config) {
  struct ddhcp_mcast_packet* packet = calloc(1, sizeof(struct ddhcp_mcast_packet));

  if (!packet) {
    return NULL;
  }

  memcpy(&packet->node_id, config->node_id, 8);
  memcpy(&packet->prefix, &config->prefix, sizeof(struct in_addr));

  packet->prefix_len = config->prefix_len;
  packet->blocksize = config->block_size;
  packet->command = command;
  packet->sender = NULL;

  return packet;
}

ATTR_NONNULL_ALL ssize_t ntoh_mcast_packet(uint8_t* buffer, ssize_t len, struct ddhcp_mcast_packet* packet) {

  // Header
  copy_buf_to_var_inc(buffer, ddhcp_node_id, packet->node_id);

  // The Python implementation prefixes with a node number?
  // prefix address
  copy_buf_to_var_inc(buffer, struct in_addr, packet->prefix);

  // prefix length
  copy_buf_to_var_inc(buffer, uint8_t, packet->prefix_len);
  // size of a block
  copy_buf_to_var_inc(buffer, uint8_t, packet->blocksize);
  // the command
  copy_buf_to_var_inc(buffer, uint8_t, packet->command);
  // count of payload entries
  copy_buf_to_var_inc(buffer, uint8_t, packet->count);

  ssize_t should_len = _packet_size(packet->command, packet->count);

  if (should_len != len) {
    WARNING("ntoh_mcast_packet(...): Calculated length differs from packet length: Got %li, expected %li", len, should_len);
    return 1;
  }

  char str[INET_ADDRSTRLEN];
  inet_ntop(AF_INET, &(packet->prefix), str, INET_ADDRSTRLEN);
  DEBUG("NODE: %lu PREFIX: %s/%i BLOCKSIZE: %i COMMAND: %i ALLOCATIONS: %i\n",
        (long unsigned int) packet->node_id,
        str,
        packet->prefix_len,
        packet->blocksize,
        packet->command,
        packet->count
       );

  // Payload
  uint8_t  tmp8;
  uint16_t tmp16;
  uint32_t tmp32;
  struct ddhcp_payload* payload;

  switch (packet->command) {
  // UpdateClaim
  case DDHCP_MSG_UPDATECLAIM:
    packet->payload = calloc(packet->count, sizeof(struct ddhcp_payload));
    payload = packet->payload;

    if (payload == NULL) {
      WARNING("ntoh_mcast_packet(...): Failed to allocate packet payload\n");
      return -ENOMEM;
    }

    for (int i = 0; i < packet->count; i++) {
      copy_buf_to_var_inc(buffer, uint32_t, tmp32);
      payload->block_index = ntohl(tmp32);

      copy_buf_to_var_inc(buffer, uint16_t, tmp16);
      payload->timeout = ntohs(tmp16);

      copy_buf_to_var_inc(buffer, uint8_t, tmp8);
      payload->reserved = tmp8;

      payload++;
    }

    break;

  // InquireBlock
  case DDHCP_MSG_INQUIRE:
    packet->payload = calloc(packet->count, sizeof(struct ddhcp_payload));
    payload = packet->payload;

    if (payload == NULL) {
      WARNING("ntoh_mcast_packet(...): Failed to allocate packet payload\n");
      return -ENOMEM;
    }

    for (int i = 0; i < packet->count; i++) {
      copy_buf_to_var_inc(buffer, uint32_t, tmp32);
      payload->block_index = ntohl(tmp32);

      payload++;
    }

    break;

  // ReNEWLease
  case DDHCP_MSG_RENEWLEASE:
  case DDHCP_MSG_LEASEACK:
  case DDHCP_MSG_LEASENAK:
  case DDHCP_MSG_RELEASE:
    packet->renew_payload = calloc(1, sizeof(struct ddhcp_renew_payload));

    if (packet->renew_payload == NULL) {
      WARNING("ntoh_mcast_packet(...): Failed to allocate packet payload\n");
      return -ENOMEM;
    }

    copy_buf_to_var_inc(buffer, uint32_t, tmp32);
    packet->renew_payload->address = ntohl(tmp32);
    copy_buf_to_var_inc(buffer, uint32_t, tmp32);
    packet->renew_payload->xid = ntohl(tmp32);
    copy_buf_to_var_inc(buffer, uint32_t, tmp32);
    packet->renew_payload->lease_seconds = ntohl(tmp32);
    memcpy(&packet->renew_payload->chaddr, buffer, 16);
    break;

  default:
    DEBUG("noth_mcast_packet(...): Unknown packet type\n");
    return 2;
  }

  return 0;
}

ATTR_NONNULL_ALL int hton_packet(struct ddhcp_mcast_packet* packet, char* buffer) {

  // Header
  copy_var_to_buf_inc(buffer, ddhcp_node_id, packet->node_id);

  // The Python implementation prefixes with a node number?
  // prefix address
  copy_var_to_buf_inc(buffer, struct in_addr, packet->prefix);

  // prefix length
  copy_var_to_buf_inc(buffer, uint8_t, packet->prefix_len);
  // size of a block
  copy_var_to_buf_inc(buffer, uint8_t, packet->blocksize);
  // the command
  copy_var_to_buf_inc(buffer, uint8_t, packet->command);
  // count of payload entries
  copy_var_to_buf_inc(buffer, uint8_t, packet->count);

  uint8_t tmp8;
  uint16_t tmp16;
  uint32_t tmp32;
  struct ddhcp_payload* payload;

  switch (packet->command) {
  case DDHCP_MSG_UPDATECLAIM:
    payload = packet->payload;

    for (unsigned int index = 0; index < packet->count; index++) {
      tmp32 = htonl(payload->block_index);
      copy_var_to_buf_inc(buffer, uint32_t, tmp32);

      tmp16 = htons(payload->timeout);
      copy_var_to_buf_inc(buffer, uint16_t, tmp16);

      tmp8 = (uint8_t)payload->reserved;
      copy_var_to_buf_inc(buffer, uint8_t, tmp8);

      payload++;
    }

    break;

  case DDHCP_MSG_INQUIRE:
    payload = packet->payload;

    for (unsigned int index = 0; index < packet->count; index++) {
      tmp32 = htonl(payload->block_index);
      copy_var_to_buf_inc(buffer, uint32_t, tmp32);

      payload++;
    }

    break;

  case DDHCP_MSG_LEASEACK:
  case DDHCP_MSG_LEASENAK:
  case DDHCP_MSG_RELEASE:
  case DDHCP_MSG_RENEWLEASE:
    tmp32 = htonl(packet->renew_payload->address);
    copy_var_to_buf_inc(buffer, uint32_t, tmp32);
    tmp32 = htonl(packet->renew_payload->xid);
    copy_var_to_buf_inc(buffer, uint32_t, tmp32);
    tmp32 = htonl(packet->renew_payload->lease_seconds);
    copy_var_to_buf_inc(buffer, uint32_t, tmp32);
    memcpy(buffer, &packet->renew_payload->chaddr, 16);
    break;

  default:
    DEBUG("hton_packet(...): Unknown packet type: %i\n", packet->command);
    break;
  }

  return 0;
}

ATTR_NONNULL_ALL ssize_t send_packet_mcast(struct ddhcp_mcast_packet* packet, ddhcp_epoll_data* data) {
  size_t len = (size_t)_packet_size(packet->command, packet->count);

  char* buffer = calloc(len, 1);

  if (buffer == NULL) {
    return -1;
  }

  errno = 0;

  hton_packet(packet, buffer);

  struct sockaddr_in6 dest_addr = {
    .sin6_family = AF_INET6,
    .sin6_port = htons(DDHCP_MULTICAST_PORT),
    .sin6_scope_id = data->interface_id
  };

  memcpy(&dest_addr.sin6_addr, &in6addr_localmcast, sizeof(in6addr_localmcast));

  ssize_t bytes_send = sendto(data->fd, buffer, len, 0, (struct sockaddr*) &dest_addr, sizeof(dest_addr));

  free(buffer);

  if ( bytes_send < 0 ) {
    ERROR("send_packet_mcast(...): Failed (%i): %s\n",errno,strerror(errno));
  }

  return bytes_send;
}

ATTR_NONNULL_ALL ssize_t send_packet_direct(struct ddhcp_mcast_packet* packet, struct in6_addr* dest, ddhcp_epoll_data* data) {
  DEBUG("send_packet_direct(packet,dest,mcsocket:%i,scope:%u)\n", data->fd, data->interface_id);
  size_t len = (size_t)_packet_size(packet->command, packet->count);

  char* buffer = calloc(len, 1);

  if (buffer == NULL) {
    ERROR("send_packet_direct(...): Failed to allocate send buffer\n");
    return -1;
  }

  struct sockaddr_in6 dest_addr = {
    .sin6_family = AF_INET6,
    .sin6_port = htons(DDHCP_UNICAST_PORT),
    .sin6_scope_id = data->interface_id
  };

  memcpy(&dest_addr.sin6_addr, dest, sizeof(struct in6_addr));

#if LOG_LEVEL_LIMIT >= LOG_DEBUG
  char ipv6_sender[INET6_ADDRSTRLEN];

  DEBUG("Sending message to %s\n",
        inet_ntop(AF_INET6, dest, ipv6_sender, INET6_ADDRSTRLEN));

#endif

  hton_packet(packet, buffer);

  ssize_t bytes_send = sendto(data->fd, buffer, len, 0, (struct sockaddr*) &dest_addr, sizeof(struct sockaddr_in6));

  free(buffer);

  if ( bytes_send < 0 ) {
    ERROR("send_packet_direct(...): Failed (%i): %s\n",errno,strerror(errno));
  }

  return bytes_send;
}