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avformat/tls_openssl: fix DTLS retransmission when packet lost in blocking mode

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OpenSSL DTLS can't retransmit lost packets in blocking mode.
Switch to non-blocking mode and use DTLSv1_handle_timeout()
to properly handle DTLS handshake retransmissions.
This commit is contained in:
Nariman-Sayed
2026-02-26 22:48:39 +02:00
committed by Jack Lau
parent 261960392e
commit b20f42b156
1 changed files with 49 additions and 12 deletions
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61
libavformat/tls_openssl.c
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@@ -23,6 +23,7 @@
#include "libavutil/mem.h"
#include "network.h"
#include "os_support.h"
#include "libavutil/time.h"
#include "libavutil/random_seed.h"
#include "url.h"
#include "tls.h"
@@ -32,7 +33,11 @@
#include <openssl/ssl.h>
#include <openssl/err.h>
#include <openssl/x509v3.h>
#if HAVE_SYS_TIME_H
#include <sys/time.h>
#endif
#define DTLS_HANDSHAKE_TIMEOUT_US 30000000
/**
* Convert an EVP_PKEY to a PEM string.
*/
@@ -623,30 +628,62 @@ static void openssl_info_callback(const SSL *ssl, int where, int ret) {
static int dtls_handshake(URLContext *h)
{
int ret = 1, r0, r1;
TLSContext *c = h->priv_data;
int ret, err;
int timeout_ms;
struct timeval timeout;
int64_t timeout_start = av_gettime_relative();
int sockfd = ffurl_get_file_handle(c->tls_shared.udp);
struct pollfd pfd = { .fd = sockfd, .events = POLLIN, .revents = 0 };
c->tls_shared.udp->flags &= ~AVIO_FLAG_NONBLOCK;
/* Force NONBLOCK mode to handle DTLS retransmissions */
c->tls_shared.udp->flags |= AVIO_FLAG_NONBLOCK;
r0 = SSL_do_handshake(c->ssl);
if (r0 <= 0) {
r1 = SSL_get_error(c->ssl, r0);
if (r1 != SSL_ERROR_WANT_READ && r1 != SSL_ERROR_WANT_WRITE && r1 != SSL_ERROR_ZERO_RETURN) {
av_log(c, AV_LOG_ERROR, "Handshake failed, r0=%d, r1=%d\n", r0, r1);
ret = print_ssl_error(h, r0);
for (;;) {
if (av_gettime_relative() - timeout_start > DTLS_HANDSHAKE_TIMEOUT_US) {
ret = AVERROR(ETIMEDOUT);
goto end;
}
} else {
av_log(c, AV_LOG_TRACE, "Handshake success, r0=%d\n", r0);
}
ret = SSL_do_handshake(c->ssl);
if (ret == 1) {
av_log(c, AV_LOG_TRACE, "Handshake success\n");
break;
}
err = SSL_get_error(c->ssl, ret);
if (err != SSL_ERROR_WANT_READ && err != SSL_ERROR_WANT_WRITE && err != SSL_ERROR_ZERO_RETURN) {
av_log(c, AV_LOG_ERROR, "Handshake failed, ret=%d, err=%d\n", ret, err);
ret = print_ssl_error(h, ret);
goto end;
}
timeout_ms = 1000;
if (DTLSv1_get_timeout(c->ssl, &timeout))
timeout_ms = timeout.tv_sec * 1000 + timeout.tv_usec / 1000;
ret = poll(&pfd, 1, timeout_ms);
if (ret > 0 && (pfd.revents & POLLIN))
continue;
if (!ret) {
if (DTLSv1_handle_timeout(c->ssl) < 0) {
ret = AVERROR(EIO);
goto end;
}
continue;
}
if (ret < 0) {
ret = ff_neterrno();
goto end;
}
}
/* Check whether the handshake is completed. */
if (SSL_is_init_finished(c->ssl) != TLS_ST_OK)
goto end;
ret = 0;
end:
if (!(h->flags & AVIO_FLAG_NONBLOCK))
c->tls_shared.udp->flags &= ~AVIO_FLAG_NONBLOCK;
return ret;
}