bird/proto/rpki/packets.c

/*
 *	BIRD -- The Resource Public Key Infrastructure (RPKI) to Router Protocol
 *
 *	(c) 2015 CZ.NIC
 *	(c) 2015 Pavel Tvrdik <pawel.tvrdik@gmail.com>
 *
 *	This file was a part of RTRlib: http://rpki.realmv6.org/
 *
 *	Can be freely distributed and used under the terms of the GNU GPL.
 */

#include <stdlib.h>
#include <string.h>
#include <stdio.h>

#undef LOCAL_DEBUG

#include "rpki.h"
#include "transport.h"
#include "packets.h"

#define RPKI_ADD_FLAG 		0b00000001

enum rpki_transmit_type {
  RPKI_RECV 			= 0,
  RPKI_SEND 			= 1,
};

enum pdu_error_type {
  CORRUPT_DATA 			= 0,
  INTERNAL_ERROR 		= 1,
  NO_DATA_AVAIL 		= 2,
  INVALID_REQUEST 		= 3,
  UNSUPPORTED_PROTOCOL_VER 	= 4,
  UNSUPPORTED_PDU_TYPE 		= 5,
  WITHDRAWAL_OF_UNKNOWN_RECORD 	= 6,
  DUPLICATE_ANNOUNCEMENT 	= 7,
  PDU_TOO_BIG 			= 32
};

static const char *str_pdu_error_type[] = {
  [CORRUPT_DATA] 		= "Corrupt-Data",
  [INTERNAL_ERROR] 		= "Internal-Error",
  [NO_DATA_AVAIL] 		= "No-Data-Available",
  [INVALID_REQUEST] 		= "Invalid-Request",
  [UNSUPPORTED_PROTOCOL_VER] 	= "Unsupported-Protocol-Version",
  [UNSUPPORTED_PDU_TYPE] 	= "Unsupported-PDU-Type",
  [WITHDRAWAL_OF_UNKNOWN_RECORD]= "Withdrawal-Of-Unknown-Record",
  [DUPLICATE_ANNOUNCEMENT] 	= "Duplicate-Announcement",
  [PDU_TOO_BIG] 		= "PDU-Too-Big",
};

enum pdu_type {
  SERIAL_NOTIFY 		= 0,
  SERIAL_QUERY 			= 1,
  RESET_QUERY 			= 2,
  CACHE_RESPONSE 		= 3,
  IPV4_PREFIX 			= 4,
  RESERVED 			= 5,
  IPV6_PREFIX			= 6,
  END_OF_DATA 			= 7,
  CACHE_RESET 			= 8,
  ROUTER_KEY 			= 9,
  ERROR 			= 10,
  ASPA				= 11,
  PDU_TYPE_MAX
};

static const char *str_pdu_type_[] = {
  [SERIAL_NOTIFY] 		= "Serial Notify",
  [SERIAL_QUERY] 		= "Serial Query",
  [RESET_QUERY] 		= "Reset Query",
  [CACHE_RESPONSE] 		= "Cache Response",
  [IPV4_PREFIX] 		= "IPv4 Prefix",
  [RESERVED] 			= "Reserved",
  [IPV6_PREFIX] 		= "IPv6 Prefix",
  [END_OF_DATA] 		= "End of Data",
  [CACHE_RESET] 		= "Cache Reset",
  [ROUTER_KEY] 			= "Router Key",
  [ERROR] 			= "Error",
  [ASPA]			= "ASPA",
};

static const char *str_pdu_type(uint type) {
  if (type < PDU_TYPE_MAX)
    return str_pdu_type_[type];
  else
    return "Undefined packet type";
}

/*
 *  0          8          16         24        31
 * .-------------------------------------------.
 * | Protocol |   PDU    |                     |
 * | Version  |   Type   |    reserved = zero  |
 * |  0 or 1  |  0 - 10  |                     |
 * +-------------------------------------------+
 * |                                           |
 * |                 Length >= 8               |
 * |                                           |
 * `-------------------------------------------' */
struct pdu_header {
  u8 ver;
  u8 type;
  u16 reserved;
  u32 len;
} PACKED;

struct pdu_cache_response {
  u8 ver;
  u8 type;
  u16 session_id;
  u32 len;
} PACKED;

struct pdu_serial_notify {
  u8 ver;
  u8 type;
  u16 session_id;
  u32 len;
  u32 serial_num;
} PACKED;

struct pdu_serial_query {
  u8 ver;
  u8 type;
  u16 session_id;
  u32 len;
  u32 serial_num;
} PACKED;

struct pdu_ipv4 {
  u8 ver;
  u8 type;
  u16 reserved;
  u32 len;
  u8 flags;
  u8 prefix_len;
  u8 max_prefix_len;
  u8 zero;
  ip4_addr prefix;
  u32 asn;
} PACKED;

struct pdu_ipv6 {
  u8 ver;
  u8 type;
  u16 reserved;
  u32 len;
  u8 flags;
  u8 prefix_len;
  u8 max_prefix_len;
  u8 zero;
  ip6_addr prefix;
  u32 asn;
} PACKED;

/*
 *  0          8          16         24        31
 *  .-------------------------------------------.
 *  | Protocol |   PDU    |                     |
 *  | Version  |   Type   |     Error Code      |
 *  |    1     |    10    |                     |
 *  +-------------------------------------------+
 *  |                                           |
 *  |                  Length                   |
 *  |                                           |
 *  +-------------------------------------------+
 *  |                                           |
 *  |       Length of Encapsulated PDU          |
 *  |                                           |
 *  +-------------------------------------------+
 *  |                                           |
 *  ~           Copy of Erroneous PDU           ~
 *  |                                           |
 *  +-------------------------------------------+
 *  |                                           |
 *  |           Length of Error Text            |
 *  |                                           |
 *  +-------------------------------------------+
 *  |                                           |
 *  |              Arbitrary Text               |
 *  |                    of                     |
 *  ~          Error Diagnostic Message         ~
 *  |                                           |
 *  `-------------------------------------------' */
struct pdu_error {
  u8 ver;
  u8 type;
  u16 error_code;
  u32 len;
  u32 len_enc_pdu;		/* Length of Encapsulated PDU */
  byte rest[];			/* Copy of Erroneous PDU
				 * Length of Error Text
				 * Error Diagnostic Message */
} PACKED;

/*
 *0          8          16         24        31
 *  .-------------------------------------------.
 *  | Protocol |   PDU    |          |          |
 *  | Version  |   Type   |   Flags  |   zero   |
 *  |    2     |    11    |          |          |
 *  +-------------------------------------------+
 *  |                                           |
 *  |                 Length                    |
 *  |                                           |
 *  +-------------------------------------------+
 *  |                                           |
 *  |    Customer Autonomous System Number      |
 *  |                                           |
 *  +-------------------------------------------+
 *  |                                           |
 *  ~    Provider Autonomous System Numbers     ~
 *  |                                           |
 *  ~-------------------------------------------~ */
struct pdu_aspa {
  u8 ver;
  u8 type;
  u8 flags;
  u8 zero;
  u32 len;
  u32 customer_as_num;
  u32 provider_as_nums[0];
} PACKED;

struct pdu_reset_query {
  u8 ver;
  u8 type;
  u16 flags;
  u32 len;
} PACKED;

struct pdu_end_of_data_v0 {
  u8 ver;
  u8 type;
  u16 session_id;
  u32 len;
  u32 serial_num;
} PACKED;

struct pdu_end_of_data_v1 {
  u8 ver;
  u8 type;
  u16 session_id;
  u32 len;
  u32 serial_num;
  u32 refresh_interval;
  u32 retry_interval;
  u32 expire_interval;
} PACKED;

static const size_t min_pdu_size[] = {
  [SERIAL_NOTIFY] 		= sizeof(struct pdu_serial_notify),
  [SERIAL_QUERY] 		= sizeof(struct pdu_serial_query),
  [RESET_QUERY] 		= sizeof(struct pdu_reset_query),
  [CACHE_RESPONSE] 		= sizeof(struct pdu_cache_response),
  [IPV4_PREFIX] 		= sizeof(struct pdu_ipv4),
  [RESERVED] 			= sizeof(struct pdu_header),
  [IPV6_PREFIX] 		= sizeof(struct pdu_ipv6),
  [END_OF_DATA] 		= sizeof(struct pdu_end_of_data_v0),
  [CACHE_RESET] 		= sizeof(struct pdu_cache_response),
  [ROUTER_KEY] 			= sizeof(struct pdu_header), /* FIXME */
  [ASPA]			= sizeof(struct pdu_aspa),
  [ERROR] 			= 16,
};

static inline int rpki_pdu_aspa_provider_asn_count(const struct pdu_aspa *pdu)
{ return (pdu->len - sizeof(struct pdu_aspa)) / (sizeof(u32)); }

static int rpki_send_error_pdu_(struct rpki_cache *cache, const enum pdu_error_type error_code, const u32 err_pdu_len, const struct pdu_header *erroneous_pdu, const char *fmt, ...);

#define rpki_send_error_pdu(cache, error_code, err_pdu_len, erroneous_pdu, fmt...) ({ \
    rpki_send_error_pdu_(cache, error_code, err_pdu_len, erroneous_pdu, #fmt); \
    CACHE_TRACE(D_PACKETS, cache, #fmt); \
    })

static void
rpki_pdu_to_network_byte_order(struct pdu_header *pdu)
{
  pdu->reserved = htons(pdu->reserved);
  pdu->len = htonl(pdu->len);

  switch (pdu->type)
  {
  case SERIAL_QUERY:
  {
    /* Note that a session_id is converted using converting header->reserved */
    struct pdu_serial_query *sq_pdu = (void *) pdu;
    sq_pdu->serial_num = htonl(sq_pdu->serial_num);
    break;
  }

  case ERROR:
  {
    struct pdu_error *err = (void *) pdu;
    u32 *err_text_len = (u32 *)(err->rest + err->len_enc_pdu);
    *err_text_len = htonl(*err_text_len);
    err->len_enc_pdu = htonl(err->len_enc_pdu);
    break;
  }

  case RESET_QUERY:
    break;

  default:
    bug("PDU type %s should not be sent by us", str_pdu_type(pdu->type));
  }
}

static void
rpki_pdu_to_host_byte_order(struct pdu_header *pdu)
{
  pdu->len = ntohl(pdu->len);

  switch (pdu->type)
  {
  case SERIAL_NOTIFY:
  {
    struct pdu_serial_notify *sn_pdu = (void *) pdu;
    sn_pdu->session_id = ntohs(sn_pdu->session_id);
    sn_pdu->serial_num = ntohl(sn_pdu->serial_num);
    break;
  }

  case END_OF_DATA:
  {
    struct pdu_end_of_data_v0 *eod0 = (void *) pdu;
    eod0->session_id = ntohs(eod0->session_id);
    eod0->serial_num = ntohl(eod0->serial_num); /* Same either for version 1 */

    if (pdu->ver > RPKI_VERSION_0)
    {
      struct pdu_end_of_data_v1 *eod1 = (void *) pdu;
      eod1->expire_interval = ntohl(eod1->expire_interval);
      eod1->refresh_interval = ntohl(eod1->refresh_interval);
      eod1->retry_interval = ntohl(eod1->retry_interval);
    }
    break;
  }

  case IPV4_PREFIX:
  {
    struct pdu_ipv4 *ipv4 = (void *) pdu;
    ipv4->prefix = ip4_ntoh(ipv4->prefix);
    ipv4->asn = ntohl(ipv4->asn);
    break;
  }

  case IPV6_PREFIX:
  {
    struct pdu_ipv6 *ipv6 = (void *) pdu;
    ipv6->prefix = ip6_ntoh(ipv6->prefix);
    ipv6->asn = ntohl(ipv6->asn);
    break;
  }

  case ERROR:
  {
    struct pdu_error *err = (void *) pdu;
    err->error_code = ntohs(err->error_code);
    err->len_enc_pdu = ntohl(err->len_enc_pdu);
    u32 *err_text_len = (u32 *)(err->rest + err->len_enc_pdu);
    *err_text_len = htonl(*err_text_len);
    break;
  }

  case ASPA:
  {
    struct pdu_aspa *aspa = (void *) pdu;
    int provider_asn_count = rpki_pdu_aspa_provider_asn_count(aspa);

    /* Convert customer ASN */
    aspa->customer_as_num = ntohl(aspa->customer_as_num);

    /* Convert provider ASNs */
    for (int i = 0; i < provider_asn_count ; i++)
      aspa->provider_as_nums[i] = ntohl(aspa->provider_as_nums[i]);

    break;
  }

  case ROUTER_KEY:
    /* Router Key PDU is not supported yet */

  case SERIAL_QUERY:
  case RESET_QUERY:
    /* Serial/Reset Query are sent only in direction router to cache.
     * We don't care here. */

  case CACHE_RESPONSE:
  {
    struct pdu_cache_response *cr = (void *) pdu;
    cr->session_id = ntohs(cr->session_id);
    break;
  }

  case CACHE_RESET:
    /* Nothing to convert */
    break;
  }
}

/**
 * rpki_convert_pdu_back_to_network_byte_order - convert host-byte order PDU back to network-byte order
 * @out: allocated memory for writing a converted PDU of size @in->len
 * @in: host-byte order PDU
 *
 * Assumed: |A == ntoh(ntoh(A))|
 */
static struct pdu_header *
rpki_pdu_back_to_network_byte_order(struct pdu_header *out, const struct pdu_header *in)
{
  /* Only valid for fixed-length PDUs */
  ASSERT_DIE(in->type != ERROR && in->type != ASPA);

  memcpy(out, in, in->len);
  rpki_pdu_to_host_byte_order(out);
  return out;
}

static void
rpki_log_packet(struct rpki_cache *cache, const struct pdu_header *pdu, const enum rpki_transmit_type action)
{
  if (!(cache->p->p.debug & D_PACKETS))
    return;

  const char *str_type = str_pdu_type(pdu->type);
  char detail[256];

#define SAVE(fn)		\
  do {				\
    if (fn < 0) 		\
    {				\
      bsnprintf(detail + sizeof(detail) - 16, 16, "... <too long>)"); \
      goto detail_finished;	\
    }				\
  } while(0)			\

  switch (pdu->type)
  {
  case SERIAL_NOTIFY:
  case SERIAL_QUERY:
    SAVE(bsnprintf(detail, sizeof(detail), "(session id: %u, serial number: %u)", pdu->reserved, ((struct pdu_serial_notify *) pdu)->serial_num));
    break;

  case END_OF_DATA:
  {
    const struct pdu_end_of_data_v1 *eod = (void *) pdu;
    if (eod->ver > RPKI_VERSION_0)
      SAVE(bsnprintf(detail, sizeof(detail), "(session id: %u, serial number: %u, refresh: %us, retry: %us, expire: %us)", eod->session_id, eod->serial_num, eod->refresh_interval, eod->retry_interval, eod->expire_interval));
    else
      SAVE(bsnprintf(detail, sizeof(detail), "(session id: %u, serial number: %u)", eod->session_id, eod->serial_num));
    break;
  }

  case CACHE_RESPONSE:
    SAVE(bsnprintf(detail, sizeof(detail), "(session id: %u)", pdu->reserved));
    break;

  case IPV4_PREFIX:
  {
    const struct pdu_ipv4 *ipv4 = (void *) pdu;
    SAVE(bsnprintf(detail, sizeof(detail), "(%I4/%u-%u AS%u)", ipv4->prefix, ipv4->prefix_len, ipv4->max_prefix_len, ipv4->asn));
    break;
  }

  case IPV6_PREFIX:
  {
    const struct pdu_ipv6 *ipv6 = (void *) pdu;
    SAVE(bsnprintf(detail, sizeof(detail), "(%I6/%u-%u AS%u)", ipv6->prefix, ipv6->prefix_len, ipv6->max_prefix_len, ipv6->asn));
    break;
  }

  case ROUTER_KEY:
    /* We don't support saving Router Key PDUs yet */
    SAVE(bsnprintf(detail, sizeof(detail), "(ignored)"));
    break;

  case ERROR:
  {
    const struct pdu_error *err = (void *) pdu;
    SAVE(bsnprintf(detail, sizeof(detail), "(%s", str_pdu_error_type[err->error_code]));

    /* Optional description of error */
    const u32 len_err_txt = *((u32 *) (err->rest + err->len_enc_pdu));
    if (len_err_txt > 0)
    {
      size_t expected_len = err->len_enc_pdu + len_err_txt + 16;
      if (expected_len == err->len)
      {
        char txt[len_err_txt + 1];
        char *pdu_txt = (char *) err->rest + err->len_enc_pdu + 4;
        bsnprintf(txt, sizeof(txt), "%s", pdu_txt); /* it's ensured that txt is ended with a null byte */
        SAVE(bsnprintf(detail + strlen(detail), sizeof(detail) - strlen(detail), ": '%s'", txt));
      }
      else
      {
	SAVE(bsnprintf(detail + strlen(detail), sizeof(detail) - strlen(detail), ", malformed size"));
      }
    }

    /* Optional encapsulated erroneous packet */
    if (err->len_enc_pdu)
    {
      SAVE(bsnprintf(detail + strlen(detail), sizeof(detail) - strlen(detail), ", %s packet:", str_pdu_type(((struct pdu_header *) err->rest)->type)));
      if (err->rest + err->len_enc_pdu <= (byte *)err + err->len)
      {
	for (const byte *c = err->rest; c != err->rest + err->len_enc_pdu; c++)
	  SAVE(bsnprintf(detail + strlen(detail), sizeof(detail) - strlen(detail), " %02X", *c));
      }
    }

    SAVE(bsnprintf(detail + strlen(detail), sizeof(detail) - strlen(detail), ")"));
    break;
  }

  case ASPA:
  {
    const struct pdu_aspa *aspa = (void *) pdu;
    int provider_asn_count = rpki_pdu_aspa_provider_asn_count(aspa);

    if (provider_asn_count <= 0)
      SAVE(bsnprintf(detail + strlen(detail), sizeof(detail) - strlen(detail),
	    "%u transit", aspa->customer_as_num));
    else
    {
      SAVE(bsnprintf(detail + strlen(detail), sizeof(detail) - strlen(detail),
	    "%u (providers", aspa->customer_as_num));
      for (int i = 0; i < provider_asn_count; i++)
	SAVE(bsnprintf(detail + strlen(detail), sizeof(detail) - strlen(detail),
	      " %u%c", aspa->provider_as_nums[i], (i == provider_asn_count-1) ? ')' : ','));
    }
    break;
  }

  default:
    *detail = '\0';
  }
#undef SAVE

 detail_finished:

  if (action == RPKI_RECV)
  {
    CACHE_TRACE(D_PACKETS, cache, "Received %s packet %s", str_type, detail);
  }
  else
  {
    CACHE_TRACE(D_PACKETS, cache, "Sending %s packet %s", str_type, detail);
  }

#if defined(LOCAL_DEBUG) || defined(GLOBAL_DEBUG)
  int seq = 0;
  for(const byte *c = pdu; c != pdu + pdu->len; c++)
  {
    if ((seq % 4) == 0)
      DBG("%2d: ", seq);

    DBG("  0x%02X %-3u", *c, *c);

    if ((++seq % 4) == 0)
      DBG("\n");
  }
  if ((seq % 4) != 0)
    DBG("\n");
#endif
}

static int
rpki_send_pdu(struct rpki_cache *cache, const void *pdu, const uint len)
{
  struct rpki_proto *p = cache->p;
  sock *sk = cache->tr_sock->sk;

  rpki_log_packet(cache, pdu, RPKI_SEND);

  if (sk->tbuf != sk->tpos)
  {
    RPKI_WARN(p, "Old packet overwritten in TX buffer");
  }

  if (len > sk->tbsize)
  {
    RPKI_WARN(p, "%u bytes is too much for send", len);
    ASSERT(0);
    return RPKI_ERROR;
  }

  memcpy(sk->tbuf, pdu, len);
  rpki_pdu_to_network_byte_order((void *) sk->tbuf);

  if (!sk_send(sk, len))
  {
    DBG("Cannot send just the whole data. It will be sent using a call of tx_hook()");
  }

  return RPKI_SUCCESS;
}

/**
 * rpki_check_receive_packet - make a basic validation of received RPKI PDU header
 * @cache: cache connection instance
 * @pdu: RPKI PDU in network byte order
 *
 * This function checks protocol version, PDU type, version and size. If all is all right then
 * function returns |RPKI_SUCCESS| otherwise sends Error PDU and returns
 * |RPKI_ERROR|.
 */
static int
rpki_check_receive_packet(struct rpki_cache *cache, const struct pdu_header *pdu)
{
  u32 pdu_len = ntohl(pdu->len);

  /*
   * Minimal and maximal allowed PDU size is treated in rpki_rx_hook() function.
   * @header.len corresponds to number of bytes of @pdu and
   * it is in range from RPKI_PDU_HEADER_LEN to RPKI_PDU_MAX_LEN bytes.
   */

  /* Do not handle error PDUs here, leave this task to rpki_handle_error_pdu() */
  if (pdu->ver != cache->version && pdu->type != ERROR)
  {
    /* If this is the first PDU we have received */
    if (cache->request_session_id)
    {
      if (pdu->type == SERIAL_NOTIFY)
      {
	/*
	 * The router MUST ignore any Serial Notify PDUs it might receive from
	 * the cache during this initial start-up period, regardless of the
	 * Protocol Version field in the Serial Notify PDU.
	 * (https://tools.ietf.org/html/draft-ietf-sidr-rpki-rtr-rfc6810-bis-07#section-7)
	 */
      }
      else if (!cache->last_update &&
	       (pdu->ver <= RPKI_MAX_VERSION) &&
	       (pdu->ver < cache->version) &&
	       (pdu->ver >= cache->min_version)
	       )
      {
        CACHE_TRACE(D_EVENTS, cache, "Downgrade session to %s from %u to %u version", rpki_get_cache_ident(cache), cache->version, pdu->ver);
        cache->version = pdu->ver;
      }
      else
      {
        /* If this is not the first PDU we have received, something is wrong with
         * the server implementation -> Error */
	rpki_send_error_pdu(cache, UNSUPPORTED_PROTOCOL_VER, pdu_len, pdu, "PDU with unsupported Protocol version received");
	return RPKI_ERROR;
      }
    }
  }

  if ((pdu->type >= PDU_TYPE_MAX) ||
      (pdu->ver < RPKI_VERSION_1 && pdu->type == ROUTER_KEY) ||
      (pdu->ver < RPKI_VERSION_2 && pdu->type == ASPA))
  {
    rpki_send_error_pdu(cache, UNSUPPORTED_PDU_TYPE, pdu_len, pdu, "Unsupported PDU type %u received", pdu->type);
    return RPKI_ERROR;
  }

  uint min_pdu_length = min_pdu_size[pdu->type];
  if (pdu->type == END_OF_DATA && pdu->ver >= RPKI_VERSION_1)
    min_pdu_length = sizeof(struct pdu_end_of_data_v1);

  if (pdu_len < min_pdu_length)
  {
    rpki_send_error_pdu(cache, CORRUPT_DATA, pdu_len, pdu, "Received %s packet with %u bytes, but expected at least %u bytes", str_pdu_type(pdu->type), pdu_len, min_pdu_length);
    return RPKI_ERROR;
  }

  return RPKI_SUCCESS;
}

static int
rpki_handle_error_pdu(struct rpki_cache *cache, const struct pdu_error *pdu)
{
  switch (pdu->error_code)
  {
  case CORRUPT_DATA:
  case INTERNAL_ERROR:
  case INVALID_REQUEST:
  case UNSUPPORTED_PDU_TYPE:
    CACHE_TRACE(D_PACKETS, cache, "Got UNSUPPORTED_PDU_TYPE");
    rpki_cache_change_state(cache, RPKI_CS_ERROR_FATAL);
    break;

  case NO_DATA_AVAIL:
    rpki_cache_change_state(cache, RPKI_CS_ERROR_NO_DATA_AVAIL);
    break;

  case UNSUPPORTED_PROTOCOL_VER:
    CACHE_TRACE(D_PACKETS, cache, "Client uses unsupported protocol version");
    if (pdu->ver <= RPKI_MAX_VERSION &&
	pdu->ver < cache->version &&
	pdu->ver >= cache->min_version)
    {
      CACHE_TRACE(D_EVENTS, cache, "Downgrading from protocol version %d to version %d", cache->version, pdu->ver);
      cache->version = pdu->ver;
      rpki_cache_change_state(cache, RPKI_CS_FAST_RECONNECT);
    }
    else
    {
      CACHE_TRACE(D_PACKETS, cache, "Got UNSUPPORTED_PROTOCOL_VER error PDU with invalid values, " \
		  "current version: %d, PDU version: %d", cache->version, pdu->ver);
      rpki_cache_change_state(cache, RPKI_CS_ERROR_FATAL);
    }
    break;

  default:
    CACHE_TRACE(D_PACKETS, cache, "Error unknown, server sent unsupported error code %u", pdu->error_code);
    rpki_cache_change_state(cache, RPKI_CS_ERROR_FATAL);
    break;
  }

  return RPKI_SUCCESS;
}

static void
rpki_handle_serial_notify_pdu(struct rpki_cache *cache, const struct pdu_serial_notify *pdu)
{
  /* The router MUST ignore any Serial Notify PDUs it might receive from
   * the cache during this initial start-up period, regardless of the
   * Protocol Version field in the Serial Notify PDU.
   * (https://tools.ietf.org/html/draft-ietf-sidr-rpki-rtr-rfc6810-bis-07#section-7)
   */
  if (cache->request_session_id)
  {
    CACHE_TRACE(D_PACKETS, cache, "Ignore a Serial Notify packet during initial start-up period");
    return;
  }

  /* XXX Serial number should be compared using method RFC 1982 (3.2) */
  if (cache->serial_num != pdu->serial_num)
    rpki_cache_change_state(cache, RPKI_CS_SYNC_START);
}

static int
rpki_handle_cache_response_pdu(struct rpki_cache *cache, const struct pdu_cache_response *pdu)
{
  if (cache->request_session_id)
  {
    rpki_start_refresh(cache->p);
    cache->session_id = pdu->session_id;
    cache->request_session_id = 0;
  }
  else
  {
    if (cache->session_id != pdu->session_id)
    {
      byte tmp[pdu->len];
      const struct pdu_header *hton_pdu = rpki_pdu_back_to_network_byte_order((void *) tmp, (const void *) pdu);
      rpki_send_error_pdu(cache, CORRUPT_DATA, pdu->len, hton_pdu, "Wrong session_id %u in Cache Response PDU", pdu->session_id);
      rpki_cache_change_state(cache, RPKI_CS_ERROR_FATAL);
      return RPKI_ERROR;
    }
  }

  rpki_cache_change_state(cache, RPKI_CS_SYNC_RUNNING);
  return RPKI_SUCCESS;
}

/**
 * rpki_prefix_pdu_2_net_addr - convert IPv4/IPv6 Prefix PDU into net_addr_union
 * @pdu: host byte order IPv4/IPv6 Prefix PDU
 * @n: allocated net_addr_union for save ROA
 *
 * This function reads ROA data from IPv4/IPv6 Prefix PDU and
 * write them into net_addr_roa4 or net_addr_roa6 data structure.
 */
static net_addr_union *
rpki_prefix_pdu_2_net_addr(const struct pdu_header *pdu, net_addr_union *n)
{
  /*
   * Note that sizeof(net_addr_roa6) > sizeof(net_addr)
   * and thence we must use net_addr_union and not only net_addr
   */

  if (pdu->type == IPV4_PREFIX)
  {
    const struct pdu_ipv4 *ipv4 = (void *) pdu;
    n->roa4.type = NET_ROA4;
    n->roa4.length = sizeof(net_addr_roa4);
    n->roa4.prefix = ipv4->prefix;
    n->roa4.asn = ipv4->asn;
    n->roa4.pxlen = ipv4->prefix_len;
    n->roa4.max_pxlen = ipv4->max_prefix_len;
  }
  else
  {
    const struct pdu_ipv6 *ipv6 = (void *) pdu;
    n->roa6.type = NET_ROA6;
    n->roa6.length = sizeof(net_addr_roa6);
    n->roa6.prefix = ipv6->prefix;
    n->roa6.asn = ipv6->asn;
    n->roa6.pxlen = ipv6->prefix_len;
    n->roa6.max_pxlen = ipv6->max_prefix_len;
  }

  return n;
}

static int
rpki_handle_prefix_pdu(struct rpki_cache *cache, const struct pdu_header *pdu)
{
  const struct rpki_config *cf = (void *) cache->p->p.cf;

  const enum pdu_type type = pdu->type;
  ASSERT(type == IPV4_PREFIX || type == IPV6_PREFIX);

  net_addr_union addr = {};
  rpki_prefix_pdu_2_net_addr(pdu, &addr);

  if (type == IPV4_PREFIX)
  {
    if ((addr.roa4.pxlen > addr.roa4.max_pxlen) ||
	(addr.roa4.max_pxlen > IP4_MAX_PREFIX_LENGTH))
    {
      RPKI_WARN(cache->p, "Received corrupt packet from RPKI cache server: invalid pxlen or max_pxlen");
      byte tmp[pdu->len];
      const struct pdu_header *hton_pdu = rpki_pdu_back_to_network_byte_order((void *) tmp, (const void *) pdu);
      rpki_send_error_pdu(cache, CORRUPT_DATA, pdu->len, hton_pdu, "Corrupted PDU: invalid pxlen or max_pxlen");
      rpki_cache_change_state(cache, RPKI_CS_ERROR_FATAL);
      return RPKI_ERROR;
    }
  }
  else
  {
    if ((addr.roa6.pxlen > addr.roa6.max_pxlen) ||
	(addr.roa6.max_pxlen > IP6_MAX_PREFIX_LENGTH))
    {
      RPKI_WARN(cache->p, "Received corrupt packet from RPKI cache server: invalid pxlen or max_pxlen");
      byte tmp[pdu->len];
      const struct pdu_header *hton_pdu = rpki_pdu_back_to_network_byte_order((void *) tmp, (const void *) pdu);
      rpki_send_error_pdu(cache, CORRUPT_DATA, pdu->len, hton_pdu, "Corrupted PDU: invalid pxlen or max_pxlen");
      rpki_cache_change_state(cache, RPKI_CS_ERROR_FATAL);
      return RPKI_ERROR;
    }
  }

  if (cf->ignore_max_length)
  {
    if (type == IPV4_PREFIX)
      addr.roa4.max_pxlen = IP4_MAX_PREFIX_LENGTH;
    else
      addr.roa6.max_pxlen = IP6_MAX_PREFIX_LENGTH;
  }

  struct channel *channel = NULL;

  if (type == IPV4_PREFIX)
    channel = cache->p->roa4_channel;
  if (type == IPV6_PREFIX)
    channel = cache->p->roa6_channel;

  if (!channel)
  {
    CACHE_TRACE(D_ROUTES, cache, "Skip %N, missing %s channel", &addr, (type == IPV4_PREFIX ? "roa4" : "roa6"), addr);
    return RPKI_ERROR;
  }

  cache->last_rx_prefix = current_time();

  /* A place for 'flags' is same for both data structures pdu_ipv4 or pdu_ipv6  */
  struct pdu_ipv4 *pfx = (void *) pdu;
  if (pfx->flags & RPKI_ADD_FLAG)
    rpki_table_add_roa(cache, channel, &addr);
  else
    rpki_table_remove_roa(cache, channel, &addr);

  return RPKI_SUCCESS;
}

static int
rpki_handle_aspa_pdu(struct rpki_cache *cache, const struct pdu_header *pdu)
{
  struct pdu_aspa *aspa = (void *) pdu;
  struct channel *channel = cache->p->aspa_channel;
  uint providers_length = aspa->len - sizeof(struct pdu_aspa);

  if (!channel)
  {
    CACHE_TRACE(D_ROUTES, cache, "Skip AS%u, missing aspa channel", aspa->customer_as_num);
    return RPKI_ERROR;
  }

  cache->last_rx_prefix = current_time();

  if (aspa->flags & RPKI_ADD_FLAG)
    rpki_table_add_aspa(cache, channel, aspa->customer_as_num, aspa->provider_as_nums, providers_length);
  else
    rpki_table_remove_aspa(cache, channel, aspa->customer_as_num);

  return RPKI_SUCCESS;
}

static uint
rpki_check_interval(struct rpki_cache *cache, const char *(check_fn)(uint), uint interval)
{
  if (check_fn(interval))
  {
    RPKI_WARN(cache->p, "%s, received %u seconds", check_fn(interval), interval);
    return 0;
  }
  return 1;
}

static void
rpki_handle_end_of_data_pdu(struct rpki_cache *cache, const struct pdu_end_of_data_v1 *pdu)
{
  const struct rpki_config *cf = (void *) cache->p->p.cf;

  if (pdu->session_id != cache->session_id)
  {
    byte tmp[pdu->len];
    const struct pdu_header *hton_pdu = rpki_pdu_back_to_network_byte_order((void *) tmp, (const void *) pdu);
    rpki_send_error_pdu(cache, CORRUPT_DATA, pdu->len, hton_pdu, "Received Session ID %u, but expected %u", pdu->session_id, cache->session_id);
    rpki_cache_change_state(cache, RPKI_CS_ERROR_FATAL);
    return;
  }

  if (pdu->ver > RPKI_VERSION_0)
  {
    if (!cf->keep_refresh_interval && rpki_check_interval(cache, rpki_check_refresh_interval, pdu->refresh_interval))
      cache->refresh_interval = pdu->refresh_interval;

    if (!cf->keep_retry_interval && rpki_check_interval(cache, rpki_check_retry_interval, pdu->retry_interval))
          cache->retry_interval = pdu->retry_interval;

    if (!cf->keep_expire_interval && rpki_check_interval(cache, rpki_check_expire_interval, pdu->expire_interval))
      cache->expire_interval = pdu->expire_interval;

    CACHE_TRACE(D_EVENTS, cache, "New interval values: "
		"refresh: %s%us, "
		"retry: %s%us, "
		"expire: %s%us",
		(cf->keep_refresh_interval ? "keeps " : ""), cache->refresh_interval,
		(cf->keep_retry_interval ? "keeps " : ""),   cache->retry_interval,
		(cf->keep_expire_interval ? "keeps " : ""),  cache->expire_interval);
  }

  rpki_stop_refresh(cache->p);

  cache->last_update = current_time();
  cache->serial_num = pdu->serial_num;
  rpki_cache_change_state(cache, RPKI_CS_ESTABLISHED);
}

/**
 * rpki_rx_packet - process a received RPKI PDU
 * @cache: RPKI connection instance
 * @pdu: a RPKI PDU in network byte order
 */
static void
rpki_rx_packet(struct rpki_cache *cache, struct pdu_header *pdu)
{
  struct rpki_proto *p = cache->p;

  if (rpki_check_receive_packet(cache, pdu) == RPKI_ERROR)
  {
    rpki_cache_change_state(cache, RPKI_CS_ERROR_FATAL);
    return;
  }

  rpki_pdu_to_host_byte_order(pdu);
  rpki_log_packet(cache, pdu, RPKI_RECV);

  switch (pdu->type)
  {
  case RESET_QUERY:
  case SERIAL_QUERY:
    RPKI_WARN(p, "Received a %s packet that is destined for cache server", str_pdu_type(pdu->type));
    break;

  case SERIAL_NOTIFY:
    /* This is a signal to synchronize with the cache server just now */
    rpki_handle_serial_notify_pdu(cache, (void *) pdu);
    break;

  case CACHE_RESPONSE:
    rpki_handle_cache_response_pdu(cache, (void *) pdu);
    break;

  case IPV4_PREFIX:
  case IPV6_PREFIX:
    rpki_handle_prefix_pdu(cache, pdu);
    break;

  case END_OF_DATA:
    rpki_handle_end_of_data_pdu(cache, (void *) pdu);
    break;

  case CACHE_RESET:
    /* Cache cannot provide an incremental update. */
    rpki_cache_change_state(cache, RPKI_CS_NO_INCR_UPDATE_AVAIL);
    break;

  case ERROR:
    rpki_handle_error_pdu(cache, (void *) pdu);
    break;

  case ROUTER_KEY:
    /* TODO: Implement Router Key PDU handling */
    break;

  case ASPA:
    rpki_handle_aspa_pdu(cache, (void *) pdu);
    break;

  default:
    CACHE_TRACE(D_PACKETS, cache, "Received unsupported type (%u)", pdu->type);
  };
}

int
rpki_rx_hook(struct birdsock *sk, uint size)
{
  struct rpki_cache *cache = sk->data;
  struct rpki_proto *p = cache->p;

  if ((p->p.proto_state == PS_FLUSH) || (p->cache != cache))
    return 0;

  byte *pkt_start = sk->rbuf;
  byte *end = pkt_start + size;

  DBG("rx hook got %u bytes \n", size);

  while (end >= pkt_start + RPKI_PDU_HEADER_LEN)
  {
    struct pdu_header *pdu = (void *) pkt_start;
    u32 pdu_size = ntohl(pdu->len);

    if (pdu_size < RPKI_PDU_HEADER_LEN || pdu_size > RPKI_PDU_MAX_LEN)
    {
      RPKI_WARN(p, "Received invalid packet length %u, purge the whole receiving buffer", pdu_size);
      return 1; /* Purge recv buffer */
    }

    if (end < pkt_start + pdu_size)
      break;

    rpki_rx_packet(cache, pdu);

    /* It is possible that bird socket was freed/closed */
    if (p->p.proto_state == PS_FLUSH || sk != cache->tr_sock->sk)
      return 0;

    pkt_start += pdu_size;
  }

  if (pkt_start != sk->rbuf)
  {
    CACHE_DBG(cache, "Move %u bytes of a memory at the start of buffer", end - pkt_start);
    memmove(sk->rbuf, pkt_start, end - pkt_start);
    sk->rpos = sk->rbuf + (end - pkt_start);
  }

  return 0; /* Not purge sk->rbuf */
}

void
rpki_err_hook(struct birdsock *sk, int error_num)
{
  struct rpki_cache *cache = sk->data;

  if (error_num)
  {
    /* sk->err may contains a SSH error description */
    if (sk->err)
      CACHE_TRACE(D_EVENTS, cache, "Lost connection: %s", sk->err);
    else
      CACHE_TRACE(D_EVENTS, cache, "Lost connection: %M", error_num);
  }
  else
  {
    CACHE_TRACE(D_EVENTS, cache, "The other side closed a connection");
  }

  if (cache->p->cache != cache)
    return;

  rpki_cache_change_state(cache, RPKI_CS_ERROR_TRANSPORT);
}

static int
rpki_fire_tx(struct rpki_cache *cache)
{
  sock *sk = cache->tr_sock->sk;

  uint bytes_to_send = sk->tpos - sk->tbuf;
  DBG("Sending %u bytes", bytes_to_send);
  return sk_send(sk, bytes_to_send);
}

void
rpki_tx_hook(sock *sk)
{
  struct rpki_cache *cache = sk->data;

  if (cache->p->cache != cache)
    return;

  while (rpki_fire_tx(cache) > 0)
    ;
}

void
rpki_connected_hook(sock *sk)
{
  struct rpki_cache *cache = sk->data;

  if (cache->p->cache != cache)
    return;

  CACHE_TRACE(D_EVENTS, cache, "Connected");
  proto_notify_state(&cache->p->p, PS_UP);

  sk->rx_hook = rpki_rx_hook;
  sk->tx_hook = rpki_tx_hook;

  rpki_cache_change_state(cache, RPKI_CS_SYNC_START);
}

/**
 * rpki_send_error_pdu - send RPKI Error PDU
 * @cache: RPKI connection instance
 * @error_code: PDU Error type
 * @err_pdu_len: length of @erroneous_pdu
 * @erroneous_pdu: optional network byte-order PDU that invokes Error by us or NULL
 * @fmt: optional description text of error or NULL
 * @args: optional arguments for @fmt
 *
 * This function prepares Error PDU and sends it to a cache server.
 */
static int
rpki_send_error_pdu_(struct rpki_cache *cache, const enum pdu_error_type error_code, const u32 err_pdu_len, const struct pdu_header *erroneous_pdu, const char *fmt, ...)
{
  va_list args;
  char msg[128];

  /* Size including the terminating null byte ('\0') */
  int msg_len = 0;

  /* Don't send errors for erroneous error PDUs */
  if (err_pdu_len >= 2)
  {
    if (erroneous_pdu->type == ERROR)
      return RPKI_SUCCESS;
  }

  if (fmt)
  {
    va_start(args, fmt);
    msg_len = bvsnprintf(msg, sizeof(msg), fmt, args) + 1;
    va_end(args);
  }

  u32 pdu_size = 16 + err_pdu_len + msg_len;
  byte pdu[pdu_size];
  memset(pdu, 0, sizeof(pdu));

  struct pdu_error *e = (void *) pdu;
  e->ver = cache->version;
  e->type = ERROR;
  e->error_code = error_code;
  e->len = pdu_size;

  e->len_enc_pdu = err_pdu_len;
  if (err_pdu_len > 0)
    memcpy(e->rest, erroneous_pdu, err_pdu_len);

  *((u32 *)(e->rest + err_pdu_len)) = msg_len;
  if (msg_len > 0)
    memcpy(e->rest + err_pdu_len + 4, msg, msg_len);

  return rpki_send_pdu(cache, pdu, pdu_size);
}

int
rpki_send_serial_query(struct rpki_cache *cache)
{
  struct pdu_serial_query pdu = {
    .ver = cache->version,
    .type = SERIAL_QUERY,
    .session_id = cache->session_id,
    .len = sizeof(pdu),
    .serial_num = cache->serial_num
  };

  if (rpki_send_pdu(cache, &pdu, sizeof(pdu)) != RPKI_SUCCESS)
  {
    rpki_cache_change_state(cache, RPKI_CS_ERROR_TRANSPORT);
    return RPKI_ERROR;
  }

  return RPKI_SUCCESS;
}

int
rpki_send_reset_query(struct rpki_cache *cache)
{
  struct pdu_reset_query pdu = {
    .ver = cache->version,
    .type = RESET_QUERY,
    .len = sizeof(pdu),
  };

  if (rpki_send_pdu(cache, &pdu, sizeof(pdu)) != RPKI_SUCCESS)
  {
    rpki_cache_change_state(cache, RPKI_CS_ERROR_TRANSPORT);
    return RPKI_ERROR;
  }

  return RPKI_SUCCESS;
}