#include <stdio.h>
#define USE_SOCKETS
#include <openssl/objects.h>
+#include <openssl/rand.h>
#include "ssl_locl.h"
#if defined(OPENSSL_SYS_VMS)
static void get_current_time(struct timeval *t);
static int dtls1_set_handshake_header(SSL *s, int type, unsigned long len);
static int dtls1_handshake_write(SSL *s);
-const char dtls1_version_str[] = "DTLSv1" OPENSSL_VERSION_PTEXT;
int dtls1_listen(SSL *s, struct sockaddr *client);
+static unsigned int dtls1_link_min_mtu(void);
+
+/* XDTLS: figure out the right values */
+static const unsigned int g_probable_mtu[] = { 1500, 512, 256 };
const SSL3_ENC_METHOD DTLSv1_enc_data = {
tls1_enc,
if (!ssl3_new(s))
return (0);
- if ((d1 = OPENSSL_malloc(sizeof(*d1))) == NULL) {
+ if ((d1 = OPENSSL_zalloc(sizeof(*d1))) == NULL) {
ssl3_free(s);
return (0);
}
- memset(d1, 0, sizeof(*d1));
d1->buffered_messages = pqueue_new();
d1->sent_messages = pqueue_new();
#endif
}
+
+#define LISTEN_SUCCESS 2
+#define LISTEN_SEND_VERIFY_REQUEST 1
+
+
int dtls1_listen(SSL *s, struct sockaddr *client)
{
- int ret;
+ int next, n, ret = 0, clearpkt = 0;
+ unsigned char cookie[DTLS1_COOKIE_LENGTH];
+ unsigned char seq[SEQ_NUM_SIZE];
+ unsigned char *data, *p, *buf;
+ unsigned long reclen, fragoff, fraglen, msglen;
+ unsigned int rectype, versmajor, msgseq, msgtype, clientvers, cookielen;
+ BIO *rbio, *wbio;
+ BUF_MEM *bufm;
+ struct sockaddr_storage tmpclient;
+ PACKET pkt, msgpkt, msgpayload, session, cookiepkt;
/* Ensure there is no state left over from a previous invocation */
if (!SSL_clear(s))
return -1;
+ ERR_clear_error();
+
+ rbio = SSL_get_rbio(s);
+ wbio = SSL_get_wbio(s);
+
+ if(!rbio || !wbio) {
+ SSLerr(SSL_F_DTLS1_LISTEN, SSL_R_BIO_NOT_SET);
+ return -1;
+ }
+
+ /*
+ * We only peek at incoming ClientHello's until we're sure we are going to
+ * to respond with a HelloVerifyRequest. If its a ClientHello with a valid
+ * cookie then we leave it in the BIO for dtls1_accept to handle.
+ */
+ BIO_ctrl(SSL_get_rbio(s), BIO_CTRL_DGRAM_SET_PEEK_MODE, 1, NULL);
+
+ /*
+ * Note: This check deliberately excludes DTLS1_BAD_VER because that version
+ * requires the MAC to be calculated *including* the first ClientHello
+ * (without the cookie). Since DTLSv1_listen is stateless that cannot be
+ * supported. DTLS1_BAD_VER must use cookies in a stateful manner (e.g. via
+ * SSL_accept)
+ */
+ if ((s->version & 0xff00) != (DTLS1_VERSION & 0xff00)) {
+ SSLerr(SSL_F_DTLS1_LISTEN, SSL_R_UNSUPPORTED_SSL_VERSION);
+ return -1;
+ }
+
+ if (s->init_buf == NULL) {
+ if ((bufm = BUF_MEM_new()) == NULL) {
+ SSLerr(SSL_F_DTLS1_LISTEN, ERR_R_MALLOC_FAILURE);
+ return -1;
+ }
+
+ if (!BUF_MEM_grow(bufm, SSL3_RT_MAX_PLAIN_LENGTH)) {
+ BUF_MEM_free(bufm);
+ SSLerr(SSL_F_DTLS1_LISTEN, ERR_R_MALLOC_FAILURE);
+ return -1;
+ }
+ s->init_buf = bufm;
+ }
+ buf = (unsigned char *)s->init_buf->data;
+
+ do {
+ /* Get a packet */
+
+ clear_sys_error();
+ /*
+ * Technically a ClientHello could be SSL3_RT_MAX_PLAIN_LENGTH
+ * + DTLS1_RT_HEADER_LENGTH bytes long. Normally init_buf does not store
+ * the record header as well, but we do here. We've set up init_buf to
+ * be the standard size for simplicity. In practice we shouldn't ever
+ * receive a ClientHello as long as this. If we do it will get dropped
+ * in the record length check below.
+ */
+ n = BIO_read(rbio, buf, SSL3_RT_MAX_PLAIN_LENGTH);
+
+ if (n <= 0) {
+ if(BIO_should_retry(rbio)) {
+ /* Non-blocking IO */
+ goto end;
+ }
+ return -1;
+ }
+
+ /* If we hit any problems we need to clear this packet from the BIO */
+ clearpkt = 1;
+
+ if (!PACKET_buf_init(&pkt, buf, n)) {
+ SSLerr(SSL_F_DTLS1_LISTEN, ERR_R_INTERNAL_ERROR);
+ return -1;
+ }
+
+ /*
+ * Parse the received record. If there are any problems with it we just
+ * dump it - with no alert. RFC6347 says this "Unlike TLS, DTLS is
+ * resilient in the face of invalid records (e.g., invalid formatting,
+ * length, MAC, etc.). In general, invalid records SHOULD be silently
+ * discarded, thus preserving the association; however, an error MAY be
+ * logged for diagnostic purposes."
+ */
+
+ /* this packet contained a partial record, dump it */
+ if (n < DTLS1_RT_HEADER_LENGTH) {
+ SSLerr(SSL_F_DTLS1_LISTEN, SSL_R_RECORD_TOO_SMALL);
+ goto end;
+ }
+
+ if (s->msg_callback)
+ s->msg_callback(0, 0, SSL3_RT_HEADER, buf,
+ DTLS1_RT_HEADER_LENGTH, s, s->msg_callback_arg);
+
+ /* Get the record header */
+ if (!PACKET_get_1(&pkt, &rectype)
+ || !PACKET_get_1(&pkt, &versmajor)) {
+ SSLerr(SSL_F_DTLS1_LISTEN, SSL_R_LENGTH_MISMATCH);
+ goto end;
+ }
+
+ if (rectype != SSL3_RT_HANDSHAKE) {
+ SSLerr(SSL_F_DTLS1_LISTEN, SSL_R_UNEXPECTED_MESSAGE);
+ goto end;
+ }
+
+ /*
+ * Check record version number. We only check that the major version is
+ * the same.
+ */
+ if (versmajor != DTLS1_VERSION_MAJOR) {
+ SSLerr(SSL_F_DTLS1_LISTEN, SSL_R_BAD_PROTOCOL_VERSION_NUMBER);
+ goto end;
+ }
+
+ if (!PACKET_forward(&pkt, 1)
+ /* Save the sequence number: 64 bits, with top 2 bytes = epoch */
+ || !PACKET_copy_bytes(&pkt, seq, SEQ_NUM_SIZE)
+ || !PACKET_get_length_prefixed_2(&pkt, &msgpkt)
+ || PACKET_remaining(&pkt) != 0) {
+ SSLerr(SSL_F_DTLS1_LISTEN, SSL_R_LENGTH_MISMATCH);
+ goto end;
+ }
+
+ /* This is an initial ClientHello so the epoch has to be 0 */
+ if (seq[0] != 0 || seq[1] != 0) {
+ SSLerr(SSL_F_DTLS1_LISTEN, SSL_R_UNEXPECTED_MESSAGE);
+ goto end;
+ }
+
+ /* Get a pointer to the raw message for the later callback */
+ data = PACKET_data(&msgpkt);
+
+ /* Finished processing the record header, now process the message */
+ if (!PACKET_get_1(&msgpkt, &msgtype)
+ || !PACKET_get_net_3(&msgpkt, &msglen)
+ || !PACKET_get_net_2(&msgpkt, &msgseq)
+ || !PACKET_get_net_3(&msgpkt, &fragoff)
+ || !PACKET_get_net_3(&msgpkt, &fraglen)
+ || !PACKET_get_sub_packet(&msgpkt, &msgpayload, msglen)
+ || PACKET_remaining(&msgpkt) != 0) {
+ SSLerr(SSL_F_DTLS1_LISTEN, SSL_R_LENGTH_MISMATCH);
+ goto end;
+ }
+
+ if (msgtype != SSL3_MT_CLIENT_HELLO) {
+ SSLerr(SSL_F_DTLS1_LISTEN, SSL_R_UNEXPECTED_MESSAGE);
+ goto end;
+ }
+
+ /* Message sequence number can only be 0 or 1 */
+ if(msgseq > 2) {
+ SSLerr(SSL_F_DTLS1_LISTEN, SSL_R_INVALID_SEQUENCE_NUMBER);
+ goto end;
+ }
+
+ /* We don't support a fragmented ClientHello whilst listening */
+ if (fragoff != 0 || fraglen != msglen) {
+ SSLerr(SSL_F_DTLS1_LISTEN, SSL_R_FRAGMENTED_CLIENT_HELLO);
+ goto end;
+ }
+
+ if (s->msg_callback)
+ s->msg_callback(0, s->version, SSL3_RT_HANDSHAKE, data,
+ msglen + DTLS1_HM_HEADER_LENGTH, s,
+ s->msg_callback_arg);
+
+ if (!PACKET_get_net_2(&msgpayload, &clientvers)) {
+ SSLerr(SSL_F_DTLS1_LISTEN, SSL_R_LENGTH_MISMATCH);
+ goto end;
+ }
+
+ /*
+ * Verify client version is supported
+ */
+ if ((clientvers > (unsigned int)s->method->version &&
+ s->method->version != DTLS_ANY_VERSION)) {
+ SSLerr(SSL_F_DTLS1_LISTEN, SSL_R_WRONG_VERSION_NUMBER);
+ goto end;
+ }
+
+ if (!PACKET_forward(&msgpayload, SSL3_RANDOM_SIZE)
+ || !PACKET_get_length_prefixed_1(&msgpayload, &session)
+ || !PACKET_get_length_prefixed_1(&msgpayload, &cookiepkt)) {
+ SSLerr(SSL_F_DTLS1_LISTEN, SSL_R_LENGTH_MISMATCH);
+ goto end;
+ }
+
+ /*
+ * Check if we have a cookie or not. If not we need to send a
+ * HelloVerifyRequest.
+ */
+ if (PACKET_remaining(&cookiepkt) == 0) {
+ next = LISTEN_SEND_VERIFY_REQUEST;
+ } else {
+ /*
+ * We have a cookie, so lets check it.
+ */
+ if (s->ctx->app_verify_cookie_cb == NULL) {
+ SSLerr(SSL_F_DTLS1_LISTEN, SSL_R_NO_VERIFY_COOKIE_CALLBACK);
+ /* This is fatal */
+ return -1;
+ }
+ if (s->ctx->app_verify_cookie_cb(s, PACKET_data(&cookiepkt),
+ PACKET_remaining(&cookiepkt)) ==
+ 0) {
+ /*
+ * We treat invalid cookies in the same was as no cookie as
+ * per RFC6347
+ */
+ next = LISTEN_SEND_VERIFY_REQUEST;
+ } else {
+ /* Cookie verification succeeded */
+ next = LISTEN_SUCCESS;
+ }
+ }
+
+ if (next == LISTEN_SEND_VERIFY_REQUEST) {
+ /*
+ * There was no cookie in the ClientHello so we need to send a
+ * HelloVerifyRequest. If this fails we do not worry about trying
+ * to resend, we just drop it.
+ */
+
+ /*
+ * Dump the read packet, we don't need it any more. Ignore return
+ * value
+ */
+ BIO_ctrl(SSL_get_rbio(s), BIO_CTRL_DGRAM_SET_PEEK_MODE, 0, NULL);
+ BIO_read(rbio, buf, SSL3_RT_MAX_PLAIN_LENGTH);
+ BIO_ctrl(SSL_get_rbio(s), BIO_CTRL_DGRAM_SET_PEEK_MODE, 1, NULL);
+
+ /* Generate the cookie */
+ if (s->ctx->app_gen_cookie_cb == NULL ||
+ s->ctx->app_gen_cookie_cb(s, cookie, &cookielen) == 0 ||
+ cookielen > 255) {
+ SSLerr(SSL_F_DTLS1_LISTEN, SSL_R_COOKIE_GEN_CALLBACK_FAILURE);
+ /* This is fatal */
+ return -1;
+ }
+
+ p = &buf[DTLS1_RT_HEADER_LENGTH];
+ msglen = dtls_raw_hello_verify_request(p + DTLS1_HM_HEADER_LENGTH,
+ cookie, cookielen);
+
+ *p++ = DTLS1_MT_HELLO_VERIFY_REQUEST;
+
+ /* Message length */
+ l2n3(msglen, p);
+
+ /* Message sequence number is always 0 for a HelloVerifyRequest */
+ s2n(0, p);
+
+ /*
+ * We never fragment a HelloVerifyRequest, so fragment offset is 0
+ * and fragment length is message length
+ */
+ l2n3(0, p);
+ l2n3(msglen, p);
+
+ /* Set reclen equal to length of whole handshake message */
+ reclen = msglen + DTLS1_HM_HEADER_LENGTH;
+
+ /* Add the record header */
+ p = buf;
+
+ *(p++) = SSL3_RT_HANDSHAKE;
+ /*
+ * Special case: for hello verify request, client version 1.0 and we
+ * haven't decided which version to use yet send back using version
+ * 1.0 header: otherwise some clients will ignore it.
+ */
+ if (s->method->version == DTLS_ANY_VERSION) {
+ *(p++) = DTLS1_VERSION >> 8;
+ *(p++) = DTLS1_VERSION & 0xff;
+ } else {
+ *(p++) = s->version >> 8;
+ *(p++) = s->version & 0xff;
+ }
+
+ /*
+ * Record sequence number is always the same as in the received
+ * ClientHello
+ */
+ memcpy(p, seq, SEQ_NUM_SIZE);
+ p += SEQ_NUM_SIZE;
+
+ /* Length */
+ s2n(reclen, p);
+
+ /*
+ * Set reclen equal to length of whole record including record
+ * header
+ */
+ reclen += DTLS1_RT_HEADER_LENGTH;
+
+ if (s->msg_callback)
+ s->msg_callback(1, 0, SSL3_RT_HEADER, buf,
+ DTLS1_RT_HEADER_LENGTH, s, s->msg_callback_arg);
+
+ /*
+ * This is unneccessary if rbio and wbio are one and the same - but
+ * maybe they're not.
+ */
+ if(BIO_dgram_get_peer(rbio, &tmpclient) <= 0
+ || BIO_dgram_set_peer(wbio, &tmpclient) <= 0) {
+ SSLerr(SSL_F_DTLS1_LISTEN, ERR_R_INTERNAL_ERROR);
+ goto end;
+ }
+
+ if (BIO_write(wbio, buf, reclen) < (int)reclen) {
+ if(BIO_should_retry(wbio)) {
+ /*
+ * Non-blocking IO...but we're stateless, so we're just
+ * going to drop this packet.
+ */
+ goto end;
+ }
+ return -1;
+ }
+
+ if (BIO_flush(wbio) <= 0) {
+ if(BIO_should_retry(wbio)) {
+ /*
+ * Non-blocking IO...but we're stateless, so we're just
+ * going to drop this packet.
+ */
+ goto end;
+ }
+ return -1;
+ }
+ }
+ } while (next != LISTEN_SUCCESS);
+
+ /*
+ * Set expected sequence numbers to continue the handshake.
+ */
+ s->d1->handshake_read_seq = 1;
+ s->d1->handshake_write_seq = 1;
+ s->d1->next_handshake_write_seq = 1;
+ DTLS_RECORD_LAYER_set_write_sequence(&s->rlayer, seq);
+
+ /*
+ * We are doing cookie exchange, so make sure we set that option in the
+ * SSL object
+ */
SSL_set_options(s, SSL_OP_COOKIE_EXCHANGE);
- s->d1->listen = 1;
- ret = SSL_accept(s);
- if (ret <= 0)
- return ret;
+ /*
+ * Tell the state machine that we've done the initial hello verify
+ * exchange
+ */
+ ossl_statem_set_hello_verify_done(s);
- (void)BIO_dgram_get_peer(SSL_get_rbio(s), client);
- return 1;
+ if(BIO_dgram_get_peer(rbio, client) <= 0) {
+ SSLerr(SSL_F_DTLS1_LISTEN, ERR_R_INTERNAL_ERROR);
+ return -1;
+ }
+
+ ret = 1;
+ clearpkt = 0;
+end:
+ BIO_ctrl(SSL_get_rbio(s), BIO_CTRL_DGRAM_SET_PEEK_MODE, 0, NULL);
+ if (clearpkt) {
+ /* Dump this packet. Ignore return value */
+ BIO_read(rbio, buf, SSL3_RT_MAX_PLAIN_LENGTH);
+ }
+ return ret;
}
static int dtls1_set_handshake_header(SSL *s, int htype, unsigned long len)
{
return dtls1_do_write(s, SSL3_RT_HANDSHAKE);
}
+
+#ifndef OPENSSL_NO_HEARTBEATS
+int dtls1_process_heartbeat(SSL *s, unsigned char *p, unsigned int length)
+{
+ unsigned char *pl;
+ unsigned short hbtype;
+ unsigned int payload;
+ unsigned int padding = 16; /* Use minimum padding */
+
+ if (s->msg_callback)
+ s->msg_callback(0, s->version, TLS1_RT_HEARTBEAT,
+ p, length, s, s->msg_callback_arg);
+
+ /* Read type and payload length first */
+ if (1 + 2 + 16 > length)
+ return 0; /* silently discard */
+ if (length > SSL3_RT_MAX_PLAIN_LENGTH)
+ return 0; /* silently discard per RFC 6520 sec. 4 */
+
+ hbtype = *p++;
+ n2s(p, payload);
+ if (1 + 2 + payload + 16 > length)
+ return 0; /* silently discard per RFC 6520 sec. 4 */
+ pl = p;
+
+ if (hbtype == TLS1_HB_REQUEST) {
+ unsigned char *buffer, *bp;
+ unsigned int write_length = 1 /* heartbeat type */ +
+ 2 /* heartbeat length */ +
+ payload + padding;
+ int r;
+
+ if (write_length > SSL3_RT_MAX_PLAIN_LENGTH)
+ return 0;
+
+ /*
+ * Allocate memory for the response, size is 1 byte message type,
+ * plus 2 bytes payload length, plus payload, plus padding
+ */
+ buffer = OPENSSL_malloc(write_length);
+ if (buffer == NULL)
+ return -1;
+ bp = buffer;
+
+ /* Enter response type, length and copy payload */
+ *bp++ = TLS1_HB_RESPONSE;
+ s2n(payload, bp);
+ memcpy(bp, pl, payload);
+ bp += payload;
+ /* Random padding */
+ if (RAND_bytes(bp, padding) <= 0) {
+ OPENSSL_free(buffer);
+ return -1;
+ }
+
+ r = dtls1_write_bytes(s, TLS1_RT_HEARTBEAT, buffer, write_length);
+
+ if (r >= 0 && s->msg_callback)
+ s->msg_callback(1, s->version, TLS1_RT_HEARTBEAT,
+ buffer, write_length, s, s->msg_callback_arg);
+
+ OPENSSL_free(buffer);
+
+ if (r < 0)
+ return r;
+ } else if (hbtype == TLS1_HB_RESPONSE) {
+ unsigned int seq;
+
+ /*
+ * We only send sequence numbers (2 bytes unsigned int), and 16
+ * random bytes, so we just try to read the sequence number
+ */
+ n2s(pl, seq);
+
+ if (payload == 18 && seq == s->tlsext_hb_seq) {
+ dtls1_stop_timer(s);
+ s->tlsext_hb_seq++;
+ s->tlsext_hb_pending = 0;
+ }
+ }
+
+ return 0;
+}
+
+int dtls1_heartbeat(SSL *s)
+{
+ unsigned char *buf, *p;
+ int ret = -1;
+ unsigned int payload = 18; /* Sequence number + random bytes */
+ unsigned int padding = 16; /* Use minimum padding */
+
+ /* Only send if peer supports and accepts HB requests... */
+ if (!(s->tlsext_heartbeat & SSL_TLSEXT_HB_ENABLED) ||
+ s->tlsext_heartbeat & SSL_TLSEXT_HB_DONT_SEND_REQUESTS) {
+ SSLerr(SSL_F_DTLS1_HEARTBEAT, SSL_R_TLS_HEARTBEAT_PEER_DOESNT_ACCEPT);
+ return -1;
+ }
+
+ /* ...and there is none in flight yet... */
+ if (s->tlsext_hb_pending) {
+ SSLerr(SSL_F_DTLS1_HEARTBEAT, SSL_R_TLS_HEARTBEAT_PENDING);
+ return -1;
+ }
+
+ /* ...and no handshake in progress. */
+ if (SSL_in_init(s) || ossl_statem_get_in_handshake(s)) {
+ SSLerr(SSL_F_DTLS1_HEARTBEAT, SSL_R_UNEXPECTED_MESSAGE);
+ return -1;
+ }
+
+ /*-
+ * Create HeartBeat message, we just use a sequence number
+ * as payload to distuingish different messages and add
+ * some random stuff.
+ * - Message Type, 1 byte
+ * - Payload Length, 2 bytes (unsigned int)
+ * - Payload, the sequence number (2 bytes uint)
+ * - Payload, random bytes (16 bytes uint)
+ * - Padding
+ */
+ buf = OPENSSL_malloc(1 + 2 + payload + padding);
+ if (buf == NULL) {
+ SSLerr(SSL_F_DTLS1_HEARTBEAT, ERR_R_MALLOC_FAILURE);
+ return -1;
+ }
+ p = buf;
+ /* Message Type */
+ *p++ = TLS1_HB_REQUEST;
+ /* Payload length (18 bytes here) */
+ s2n(payload, p);
+ /* Sequence number */
+ s2n(s->tlsext_hb_seq, p);
+ /* 16 random bytes */
+ if (RAND_bytes(p, 16) <= 0) {
+ SSLerr(SSL_F_DTLS1_HEARTBEAT, ERR_R_INTERNAL_ERROR);
+ goto err;
+ }
+ p += 16;
+ /* Random padding */
+ if (RAND_bytes(p, padding) <= 0) {
+ SSLerr(SSL_F_DTLS1_HEARTBEAT, ERR_R_INTERNAL_ERROR);
+ goto err;
+ }
+
+ ret = dtls1_write_bytes(s, TLS1_RT_HEARTBEAT, buf, 3 + payload + padding);
+ if (ret >= 0) {
+ if (s->msg_callback)
+ s->msg_callback(1, s->version, TLS1_RT_HEARTBEAT,
+ buf, 3 + payload + padding,
+ s, s->msg_callback_arg);
+
+ dtls1_start_timer(s);
+ s->tlsext_hb_pending = 1;
+ }
+
+ err:
+ OPENSSL_free(buf);
+
+ return ret;
+}
+#endif
+
+int dtls1_shutdown(SSL *s)
+{
+ int ret;
+#ifndef OPENSSL_NO_SCTP
+ BIO *wbio;
+
+ wbio = SSL_get_wbio(s);
+ if (wbio != NULL && BIO_dgram_is_sctp(wbio) &&
+ !(s->shutdown & SSL_SENT_SHUTDOWN)) {
+ ret = BIO_dgram_sctp_wait_for_dry(wbio);
+ if (ret < 0)
+ return -1;
+
+ if (ret == 0)
+ BIO_ctrl(SSL_get_wbio(s), BIO_CTRL_DGRAM_SCTP_SAVE_SHUTDOWN, 1,
+ NULL);
+ }
+#endif
+ ret = ssl3_shutdown(s);
+#ifndef OPENSSL_NO_SCTP
+ BIO_ctrl(SSL_get_wbio(s), BIO_CTRL_DGRAM_SCTP_SAVE_SHUTDOWN, 0, NULL);
+#endif
+ return ret;
+}
+
+int dtls1_query_mtu(SSL *s)
+{
+ if (s->d1->link_mtu) {
+ s->d1->mtu =
+ s->d1->link_mtu - BIO_dgram_get_mtu_overhead(SSL_get_wbio(s));
+ s->d1->link_mtu = 0;
+ }
+
+ /* AHA! Figure out the MTU, and stick to the right size */
+ if (s->d1->mtu < dtls1_min_mtu(s)) {
+ if (!(SSL_get_options(s) & SSL_OP_NO_QUERY_MTU)) {
+ s->d1->mtu =
+ BIO_ctrl(SSL_get_wbio(s), BIO_CTRL_DGRAM_QUERY_MTU, 0, NULL);
+
+ /*
+ * I've seen the kernel return bogus numbers when it doesn't know
+ * (initial write), so just make sure we have a reasonable number
+ */
+ if (s->d1->mtu < dtls1_min_mtu(s)) {
+ /* Set to min mtu */
+ s->d1->mtu = dtls1_min_mtu(s);
+ BIO_ctrl(SSL_get_wbio(s), BIO_CTRL_DGRAM_SET_MTU,
+ s->d1->mtu, NULL);
+ }
+ } else
+ return 0;
+ }
+ return 1;
+}
+
+static unsigned int dtls1_link_min_mtu(void)
+{
+ return (g_probable_mtu[(sizeof(g_probable_mtu) /
+ sizeof(g_probable_mtu[0])) - 1]);
+}
+
+unsigned int dtls1_min_mtu(SSL *s)
+{
+ return dtls1_link_min_mtu() - BIO_dgram_get_mtu_overhead(SSL_get_wbio(s));
+}