WHIP: Update the dependency, requires openssl.

configure

@@ -3480,6 +3480,7 @@ ogg_demuxer_select="dirac_parse"
 ogv_muxer_select="ogg_muxer"
 opus_muxer_select="ogg_muxer"
 psp_muxer_select="mov_muxer"
+rtc_muxer_deps_any="openssl"
 rtp_demuxer_select="sdp_demuxer"
 rtp_mpegts_muxer_select="mpegts_muxer rtp_muxer"
 rtpdec_select="asf_demuxer mov_demuxer mpegts_demuxer rm_demuxer rtp_protocol srtp"

libavformat/rtcenc.c

@@ -19,6 +19,13 @@
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  */
 
+#include "config.h"
+
+#if CONFIG_OPENSSL
+#include <openssl/ssl.h>
+#include <openssl/err.h>
+#endif
+
 #include "libavutil/dict.h"
 #include "libavutil/avassert.h"
 #include "libavutil/mathematics.h"
@@ -632,6 +639,34 @@ static int ice_handshake(AVFormatContext *s)
     return ret;
 }
 
+#if CONFIG_OPENSSL
+/**
+ * DTLS handshake with server, as a client in active mode, using openssl.
+ *
+ * @return 0 if OK, AVERROR_xxx on error
+ */
+static int dtls_handshake_openssl(AVFormatContext *s)
+{
+    int ret = 0;
+    SSL_CTX *dtls_ctx = NULL;
+
+#if OPENSSL_VERSION_NUMBER < 0x10002000L // v1.0.2
+    dtls_ctx = SSL_CTX_new(DTLSv1_method());
+#else
+    dtls_ctx = SSL_CTX_new(DTLS_client_method());
+#endif
+    if (!dtls_ctx) {
+        av_log(s, AV_LOG_ERROR, "Failed to create DTLS context\n");
+        ret = AVERROR(ENOMEM);
+        goto end;
+    }
+
+end:
+    SSL_CTX_free(dtls_ctx);
+    return ret;
+}
+#endif
+
 static av_cold int rtc_init(AVFormatContext *s)
 {
     int ret;
@@ -658,6 +693,14 @@ static int rtc_write_header(AVFormatContext *s)
     if ((ret = ice_handshake(s)) < 0)
         return ret;
 
+#if CONFIG_OPENSSL
+    if ((ret = dtls_handshake_openssl(s)) < 0)
+        return ret;
+#else
+    av_log(s, AV_LOG_ERROR, "DTLS is not supported, please enable openssl\n");
+    return AVERROR(ENOSYS);
+#endif
+
     return ret;
 }