GNUnet  0.20.0
gnunet-service-nat_stun.h File Reference

This code provides some support for doing STUN transactions. More...

#include "platform.h"
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int GNUNET_NAT_stun_handle_packet_ (const void *data, size_t len, struct sockaddr_in *arg)
 Handle an incoming STUN response. More...

Detailed Description

This code provides some support for doing STUN transactions.

We receive the simplest possible packet as the STUN server and try to respond properly.

All STUN packets start with a simple header made of a type, length (excluding the header) and a 16-byte random transaction id. Following the header we may have zero or more attributes, each structured as a type, length and a value (whose format depends on the type, but often contains addresses). Of course all fields are in network format.

This code was based on ministun.c.

Functions for STUN functionality

Bruno Souza Cabral

Definition in file gnunet-service-nat_stun.h.

Function Documentation

◆ GNUNET_NAT_stun_handle_packet_()

int GNUNET_NAT_stun_handle_packet_ ( const void *  data,
size_t  len,
struct sockaddr_in *  arg 

Handle an incoming STUN response.

Do some basic sanity checks on packet size and content, try to extract information. At the moment this only processes BIND requests, and returns the externally visible address of the original request.

datathe packet
lenthe length of the packet in data
[out]argsockaddr_in where we will set our discovered address
GNUNET_OK on success, GNUNET_NO if the packet is invalid (not a stun packet)

Definition at line 125 of file gnunet-service-nat_stun.c.

128 {
129  const struct stun_header *hdr;
130  const struct stun_attr *attr;
131  struct StunState st;
132  uint32_t advertised_message_size;
133  uint32_t message_magic_cookie;
134  int ret = GNUNET_SYSERR;
136  /* On entry, 'len' is the length of the UDP payload. After the
137  * initial checks it becomes the size of unprocessed options,
138  * while 'data' is advanced accordingly.
139  */
140  if (len < sizeof(struct stun_header))
141  {
143  "Packet too short to be a STUN packet\n");
144  return GNUNET_NO;
145  }
146  hdr = data;
147  /* Skip header as it is already in hdr */
148  len -= sizeof(struct stun_header);
149  data += sizeof(struct stun_header);
151  /* len as advertised in the message */
152  advertised_message_size = ntohs (hdr->msglen);
153  message_magic_cookie = ntohl (hdr->magic);
154  /* Compare if the cookie match */
155  if (STUN_MAGIC_COOKIE != message_magic_cookie)
156  {
158  "Invalid magic cookie for STUN packet\n");
159  return GNUNET_NO;
160  }
163  "STUN Packet, msg %s (%04x), length: %d\n",
164  stun_msg2str (ntohs (hdr->msgtype)),
165  ntohs (hdr->msgtype),
166  advertised_message_size);
167  if (advertised_message_size > len)
168  {
170  "Scrambled STUN packet length (got %d, expecting %d)\n",
171  advertised_message_size,
172  (int) len);
173  return GNUNET_NO;
174  }
175  len = advertised_message_size;
176  memset (&st, 0, sizeof(st));
178  while (len > 0)
179  {
180  if (len < sizeof(struct stun_attr))
181  {
183  "Attribute too short (got %d, expecting %d)\n",
184  (int) len,
185  (int) sizeof(struct stun_attr));
186  break;
187  }
188  attr = (const struct stun_attr *) data;
190  /* compute total attribute length */
191  advertised_message_size = ntohs (attr->len) + sizeof(struct stun_attr);
193  /* Check if we still have space in our buffer */
194  if (advertised_message_size > len)
195  {
197  "Inconsistent attribute (length %d exceeds remaining msg len %d)\n",
198  advertised_message_size,
199  (int) len);
200  break;
201  }
202  if (GNUNET_OK ==
204  attr,
205  hdr->magic,
206  arg))
207  ret = GNUNET_OK;
208  data += advertised_message_size;
209  len -= advertised_message_size;
210  }
211  return ret;
212 }
static int ret
Return value of the commandline.
Definition: gnunet-abd.c:81
static struct GNUNET_SCHEDULER_Task * st
The shutdown task.
uint32_t data
The data value.
uint16_t len
length of data (which is always a uint32_t, but presumably this can be used to specify that fewer byt...
#define LOG(kind,...)
static int stun_get_mapped(struct StunState *st, const struct stun_attr *attr, uint32_t magic, struct sockaddr_in *arg)
Extract the STUN_MAPPED_ADDRESS from the stun response.
Definition: nat_stun.h:34
static const char * stun_msg2str(int msg)
Print a class and method from a STUN message.
Definition: nat_stun.h:173
Context for stun_get_mapped().
uint16_t attr
Definition: nat_stun.h:53
uint16_t msglen
Definition: nat_stun.h:45
uint16_t msgtype
Definition: nat_stun.h:44
uint32_t magic
Definition: nat_stun.h:46

References find_typedefs::arg, stun_attr::attr, data, GNUNET_ERROR_TYPE_DEBUG, GNUNET_ERROR_TYPE_INFO, GNUNET_NO, GNUNET_OK, GNUNET_SYSERR, len, LOG, stun_header::magic, stun_header::msglen, stun_header::msgtype, ret, st, stun_get_mapped(), STUN_MAGIC_COOKIE, and stun_msg2str().

Referenced by handle_stun().

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