tcp/transport.c

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#include "network/acip/transport.h"
#include "network/packet.h"
#include "network/network.h"
#include "log/logging.h"
#include "platform/socket.h"
#include "crypto/crypto.h"
#include "buffer_pool.h"
#include "util/endian.h"
#include "network/crc32.h"
#include <string.h>
 
typedef struct {
  socket_t sockfd;   
  bool is_connected; 
} tcp_transport_data_t;
 
// =============================================================================
// Helper Functions
// =============================================================================
 
static asciichat_error_t tcp_send_all(socket_t sockfd, const void *data, size_t len) {
  const uint8_t *ptr = (const uint8_t *)data;
  size_t remaining = len;
 
  while (remaining > 0) {
    ssize_t sent = socket_send(sockfd, ptr, remaining, 0);
    if (sent < 0) {
      return SET_ERRNO_SYS(ERROR_NETWORK, "Socket send failed (tried to send %zu bytes, %zu remaining)", len,
                           remaining);
    }
    if (sent == 0) {
      return SET_ERRNO(ERROR_NETWORK, "Socket closed (tried to send %zu bytes, %zu remaining)", len, remaining);
    }
    ptr += sent;
    remaining -= (size_t)sent;
  }
 
  return ASCIICHAT_OK;
}
 
// =============================================================================
// TCP Transport Methods
// =============================================================================
 
static asciichat_error_t tcp_send(acip_transport_t *transport, const void *data, size_t len) {
  tcp_transport_data_t *tcp = (tcp_transport_data_t *)transport->impl_data;
 
  if (!tcp->is_connected) {
    return SET_ERRNO(ERROR_NETWORK, "TCP transport not connected");
  }
 
  // Data already has packet header from send.c, so we need to extract the type
  // to determine if this is a handshake packet (which should NOT be encrypted)
  if (len < sizeof(packet_header_t)) {
    return SET_ERRNO(ERROR_NETWORK, "Packet too small: %zu < %zu", len, sizeof(packet_header_t));
  }
 
  // Extract packet type from header
  const packet_header_t *header = (const packet_header_t *)data;
  uint16_t packet_type = NET_TO_HOST_U16(header->type);
 
  // Check if encryption is needed
  bool should_encrypt = false;
  if (transport->crypto_ctx && crypto_is_ready(transport->crypto_ctx)) {
    // Handshake packets are ALWAYS sent unencrypted
    if (!packet_is_handshake_type((packet_type_t)packet_type)) {
      should_encrypt = true;
    }
  }
 
  // If no encryption needed, send raw data
  if (!should_encrypt) {
    return tcp_send_all(tcp->sockfd, data, len);
  }
 
  // Encrypt the entire packet (header + payload)
  size_t ciphertext_size = len + CRYPTO_NONCE_SIZE + CRYPTO_MAC_SIZE;
  uint8_t *ciphertext = buffer_pool_alloc(NULL, ciphertext_size);
  if (!ciphertext) {
    return SET_ERRNO(ERROR_MEMORY, "Failed to allocate ciphertext buffer");
  }
 
  size_t ciphertext_len;
  crypto_result_t result =
      crypto_encrypt(transport->crypto_ctx, data, len, ciphertext, ciphertext_size, &ciphertext_len);
  if (result != CRYPTO_OK) {
    buffer_pool_free(NULL, ciphertext, ciphertext_size);
    return SET_ERRNO(ERROR_CRYPTO, "Failed to encrypt packet: %s", crypto_result_to_string(result));
  }
 
  // Build PACKET_TYPE_ENCRYPTED header
  packet_header_t encrypted_header;
  encrypted_header.magic = HOST_TO_NET_U32(PACKET_MAGIC);
  encrypted_header.type = HOST_TO_NET_U16(PACKET_TYPE_ENCRYPTED);
  encrypted_header.length = HOST_TO_NET_U32((uint32_t)ciphertext_len);
  encrypted_header.crc32 = HOST_TO_NET_U32(asciichat_crc32(ciphertext, ciphertext_len));
  encrypted_header.client_id = 0;
 
  // Send encrypted packet: header + ciphertext
  asciichat_error_t send_result = ASCIICHAT_OK;
  send_result = tcp_send_all(tcp->sockfd, &encrypted_header, sizeof(encrypted_header));
  if (send_result == ASCIICHAT_OK) {
    send_result = tcp_send_all(tcp->sockfd, ciphertext, ciphertext_len);
  }
 
  buffer_pool_free(NULL, ciphertext, ciphertext_size);
 
  log_debug_every(LOG_RATE_SLOW, "Sent encrypted packet (original type %d as PACKET_TYPE_ENCRYPTED)", packet_type);
  return send_result;
}
 
static asciichat_error_t tcp_recv(acip_transport_t *transport, void **buffer, size_t *out_len,
                                  void **out_allocated_buffer) {
  tcp_transport_data_t *tcp = (tcp_transport_data_t *)transport->impl_data;
 
  if (!tcp->is_connected) {
    return SET_ERRNO(ERROR_NETWORK, "TCP transport not connected");
  }
 
  // Use secure packet receive with envelope
  packet_envelope_t envelope;
  bool enforce_encryption = (transport->crypto_ctx != NULL);
  packet_recv_result_t result =
      receive_packet_secure(tcp->sockfd, transport->crypto_ctx, enforce_encryption, &envelope);
 
  if (result != PACKET_RECV_SUCCESS) {
    if (result == PACKET_RECV_EOF) {
      return SET_ERRNO(ERROR_NETWORK, "Connection closed");
    } else if (result == PACKET_RECV_SECURITY_VIOLATION) {
      return SET_ERRNO(ERROR_CRYPTO, "Security violation");
    } else {
      return SET_ERRNO(ERROR_NETWORK, "Failed to receive packet");
    }
  }
 
  *buffer = envelope.data;
  *out_len = envelope.len;
  *out_allocated_buffer = envelope.allocated_buffer;
 
  return ASCIICHAT_OK;
}
 
static asciichat_error_t tcp_close(acip_transport_t *transport) {
  tcp_transport_data_t *tcp = (tcp_transport_data_t *)transport->impl_data;
 
  if (!tcp->is_connected) {
    return ASCIICHAT_OK; // Already closed
  }
 
  // Note: We do NOT close the socket - caller owns it
  // We just mark ourselves as disconnected
  tcp->is_connected = false;
 
  log_debug("TCP transport marked as disconnected (socket not closed)");
  return ASCIICHAT_OK;
}
 
static acip_transport_type_t tcp_get_type(acip_transport_t *transport) {
  (void)transport;
  return ACIP_TRANSPORT_TCP;
}
 
static socket_t tcp_get_socket(acip_transport_t *transport) {
  tcp_transport_data_t *tcp = (tcp_transport_data_t *)transport->impl_data;
  return tcp->sockfd;
}
 
static bool tcp_is_connected(acip_transport_t *transport) {
  tcp_transport_data_t *tcp = (tcp_transport_data_t *)transport->impl_data;
  return tcp->is_connected;
}
 
// =============================================================================
// TCP Transport Method Table
// =============================================================================
 
static const acip_transport_methods_t tcp_methods = {
    .send = tcp_send,
    .recv = tcp_recv,
    .close = tcp_close,
    .get_type = tcp_get_type,
    .get_socket = tcp_get_socket,
    .is_connected = tcp_is_connected,
    .destroy_impl = NULL, // No custom cleanup needed
};
 
// =============================================================================
// TCP Transport Creation
// =============================================================================
 
acip_transport_t *acip_tcp_transport_create(socket_t sockfd, crypto_context_t *crypto_ctx) {
  if (sockfd == INVALID_SOCKET_VALUE) {
    SET_ERRNO(ERROR_INVALID_PARAM, "Invalid socket descriptor");
    return NULL;
  }
 
  // Allocate transport structure
  acip_transport_t *transport = SAFE_MALLOC(sizeof(acip_transport_t), acip_transport_t *);
  if (!transport) {
    SET_ERRNO(ERROR_MEMORY, "Failed to allocate TCP transport");
    return NULL;
  }
 
  // Allocate TCP-specific data
  tcp_transport_data_t *tcp_data = SAFE_MALLOC(sizeof(tcp_transport_data_t), tcp_transport_data_t *);
  if (!tcp_data) {
    SAFE_FREE(transport);
    SET_ERRNO(ERROR_MEMORY, "Failed to allocate TCP transport data");
    return NULL;
  }
 
  // Initialize TCP data
  tcp_data->sockfd = sockfd;
  tcp_data->is_connected = true;
 
  // Initialize transport
  transport->methods = &tcp_methods;
  transport->crypto_ctx = crypto_ctx;
  transport->impl_data = tcp_data;
 
  log_debug("Created TCP transport for socket %d (crypto: %s)", sockfd, crypto_ctx ? "enabled" : "disabled");
 
  return transport;
}
 
// =============================================================================
// Transport Destroy (shared implementation)
// =============================================================================
 
void acip_transport_destroy(acip_transport_t *transport) {
  if (!transport) {
    return;
  }
 
  // Close if still connected
  if (transport->methods && transport->methods->close && transport->methods->is_connected &&
      transport->methods->is_connected(transport)) {
    transport->methods->close(transport);
  }
 
  // Call custom destroy implementation if provided
  if (transport->methods && transport->methods->destroy_impl) {
    transport->methods->destroy_impl(transport);
  }
 
  // Free implementation data
  if (transport->impl_data) {
    SAFE_FREE(transport->impl_data);
  }
 
  // Free transport structure
  SAFE_FREE(transport);
 
  log_debug("Destroyed ACIP transport");
}