Index: channels/chan_sip.c
===================================================================
--- channels/chan_sip.c	(revision 12340)
+++ channels/chan_sip.c	(arbetskopia)
@@ -115,8 +115,12 @@
 #define SRTP_MASTERSALT_LEN (SRTP_MASTER_LEN - SRTP_MASTERKEY_LEN)
 #define SRTP_MASTER_LEN64 ((SRTP_MASTER_LEN * 8 + 5) / 6 + 1)
 
+/* SRTP flags */
+#define SRTP_ENCR_OPTIONAL	1	/* SRTP encryption optional */
+
 /*! \brief structure for secure RTP audio */
 struct sip_srtp {
+	unsigned int flags;
 	char *a_crypto;
 	unsigned char local_key[SRTP_MASTER_LEN];
 	char local_key64[SRTP_MASTER_LEN64];
@@ -2147,6 +2151,11 @@
 	if (!ast_srtp_is_registered())
 		return -1;
 
+	if (ast_test_flag(p, SIP_OUTGOING) && !srtp) {
+		ast_log(LOG_WARNING, "Ignoring unexpected crypto attribute in SDP answer\n");
+		return -1;
+	}
+
 	/* Crypto already accepted */
 	if (srtp && srtp->a_crypto)
 		return -1;
@@ -2284,6 +2293,11 @@
 					ast_log(LOG_WARNING, "SIP SRTP sdes setup failed\n");
 					return -1;
 				}
+
+				if (!strcasecmp(ast_var_value(current), "optional")) {
+					ast_set_flag(p->srtp, SRTP_ENCR_OPTIONAL);
+				}
+
 			}
 		}
 
@@ -4708,6 +4722,7 @@
 	int debug;
 	const char *protocol = NULL;
 	struct sip_srtp *srtp = p->srtp;
+	const char a_encr_optional[] = "a=encryption:optional\r\n";
 	
 	debug = sip_debug_test_pvt(p);
 
@@ -4765,7 +4780,7 @@
 		}
 	}
 
-	if (a_crypto) {
+	if (a_crypto && !ast_test_flag(srtp, SRTP_ENCR_OPTIONAL)) {
 		protocol = "SAVP";
 	} else {
 		protocol = "AVP";
@@ -4864,8 +4879,12 @@
 	if ((p->vrtp) && (!ast_test_flag(p, SIP_NOVIDEO)) && (capability & VIDEO_CODEC_MASK)) /* only if video response is appropriate */
 		len += strlen(m_video) + strlen(a_video);
 
-	if (a_crypto)
+	if (a_crypto) {
 		len += strlen(a_crypto);
+		if (ast_test_flag(srtp, SRTP_ENCR_OPTIONAL)) {
+			len += strlen(a_encr_optional);
+		}
+	}
 
 	add_header(resp, "Content-Type", "application/sdp");
 	add_header_contentLength(resp, len);
@@ -4876,8 +4895,12 @@
 	add_line(resp, t);
 	add_line(resp, m_audio);
 	add_line(resp, a_audio);
-	if (a_crypto)
+	if (a_crypto) {
 	    add_line(resp, a_crypto);
+	    if (ast_test_flag(srtp, SRTP_ENCR_OPTIONAL)) {
+		    add_line(resp, a_encr_optional);
+	    }
+	}
 	if ((p->vrtp) && (!ast_test_flag(p, SIP_NOVIDEO)) && (capability & VIDEO_CODEC_MASK)) { /* only if video response is appropriate */
 		add_line(resp, m_video);
 		add_line(resp, a_video);