]> git.ipfire.org Git - thirdparty/asterisk.git/commitdiff
Issues with DTMF triggered attended transfers.
authorRichard Mudgett <rmudgett@digium.com>
Tue, 18 Jan 2011 18:04:36 +0000 (18:04 +0000)
committerRichard Mudgett <rmudgett@digium.com>
Tue, 18 Jan 2011 18:04:36 +0000 (18:04 +0000)
Issue #17999
1) A calls B. B answers.
2) B using DTMF dial *2 (code in features.conf for attended transfer).
3) A hears MOH. B dial number C
4) C ringing. A hears MOH.
5) B hangup. A still hears MOH. C ringing.
6) A hangup. C still ringing until "atxfernoanswertimeout" expires.
For v1.4 C will ring forever until C answers the dead line. (Issue #17096)

Problem: When A and B hangup, C is still ringing.

Issue #18395
SIP call limit of B is 1
1. A call B, B answered
2. B *2(atxfer) call C
3. B hangup, C ringing
4. Timeout waiting for C to answer
5. Recall to B fails because B has reached its call limit.

Because B reached its call limit, it cannot do anything until the transfer
it started completes.

Issue #17273
Same scenario as issue 18395 but party B is an FXS port.  Party B cannot
do anything until the transfer it started completes.  If B goes back off
hook before C answers, B hears ringback instead of the expected dialtone.

**********
Note for the issue #17273 and #18395 fix:

DTMF attended transfer works within the channel bridge.  Unfortunately,
when either party A or B in the channel bridge hangs up, that channel is
not completely hung up until the transfer completes.  This is a real
problem depending upon the channel technology involved.

For chan_dahdi, the channel is crippled until the hangup is complete.
Either the channel is not useable (analog) or the protocol disconnect
messages are held up (PRI/BRI/SS7) and the media is not released.

For chan_sip, a call limit of one is going to block that endpoint from any
further calls until the hangup is complete.

For party A this is a minor problem.  The party A channel will only be in
this condition while party B is dialing and when party B and C are
conferring.  The conversation between party B and C is expected to be a
short one.  Party B is either asking a question of party C or announcing
party A.  Also party A does not have much incentive to hangup at this
point.

For party B this can be a major problem during a blonde transfer.  (A
blonde transfer is our term for an attended transfer that is converted
into a blind transfer.  :)) Party B could be the operator.  When party B
hangs up, he assumes that he is out of the original call entirely.  The
party B channel will be in this condition while party C is ringing, while
attempting to recall party B, and while waiting between call attempts.

WARNING:
The ATXFER_NULL_TECH conditional is a hack to fix the problem.  It will
replace the party B channel technology with a NULL channel driver to
complete hanging up the party B channel technology.  The consequences of
this code is that the 'h' extension will not be able to access any channel
technology specific information like SIP statistics for the call.

ATXFER_NULL_TECH is not defined by default.
**********

(closes issue #17999)
Reported by: iskatel
Tested by: rmudgett
JIRA SWP-2246

(closes issue #17096)
Reported by: gelo
Tested by: rmudgett
JIRA SWP-1192

(closes issue #18395)
Reported by: shihchuan
Tested by: rmudgett

(closes issue #17273)
Reported by: grecco
Tested by: rmudgett

Review: https://reviewboard.asterisk.org/r/1047/

git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/1.4@302172 65c4cc65-6c06-0410-ace0-fbb531ad65f3

res/res_features.c

index 893d0fac1439457e29833cf819d46f2d0f19f931..e62339405bb0c8cf2901e0825d8888adb5bdb713 100644 (file)
@@ -66,6 +66,54 @@ ASTERISK_FILE_VERSION(__FILE__, "$Revision$")
 #include "asterisk/monitor.h"
 #include "asterisk/global_datastores.h"
 
+/*
+ * Party A - transferee
+ * Party B - transferer
+ * Party C - target of transfer
+ *
+ * DTMF attended transfer works within the channel bridge.
+ * Unfortunately, when either party A or B in the channel bridge
+ * hangs up, that channel is not completely hung up until the
+ * transfer completes.  This is a real problem depending upon
+ * the channel technology involved.
+ *
+ * For chan_dahdi, the channel is crippled until the hangup is
+ * complete.  Either the channel is not useable (analog) or the
+ * protocol disconnect messages are held up (PRI) and
+ * the media is not released.
+ *
+ * For chan_sip, a call limit of one is going to block that
+ * endpoint from any further calls until the hangup is complete.
+ *
+ * For party A this is a minor problem.  The party A channel
+ * will only be in this condition while party B is dialing and
+ * when party B and C are conferring.  The conversation between
+ * party B and C is expected to be a short one.  Party B is
+ * either asking a question of party C or announcing party A.
+ * Also party A does not have much incentive to hangup at this
+ * point.
+ *
+ * For party B this can be a major problem during a blonde
+ * transfer.  (A blonde transfer is our term for an attended
+ * transfer that is converted into a blind transfer. :))  Party
+ * B could be the operator.  When party B hangs up, he assumes
+ * that he is out of the original call entirely.  The party B
+ * channel will be in this condition while party C is ringing.
+ *
+ * WARNING:
+ * The ATXFER_NULL_TECH conditional is a hack to fix the
+ * problem.  It will replace the party B channel technology with
+ * a NULL channel driver.  The consequences of this code is that
+ * the 'h' extension will not be able to access any channel
+ * technology specific information like SIP statistics for the
+ * call.
+ *
+ * Uncomment the ATXFER_NULL_TECH define below to replace the
+ * party B channel technology in the channel bridge to complete
+ * hanging up the channel technology.
+ */
+//#define ATXFER_NULL_TECH     1
+
 #define DEFAULT_PARK_TIME 45000
 #define DEFAULT_TRANSFER_DIGIT_TIMEOUT 3000
 #define DEFAULT_FEATURE_DIGIT_TIMEOUT 1000
@@ -179,6 +227,119 @@ struct ast_dial_features {
        int is_caller;
 };
 
+#if defined(ATXFER_NULL_TECH)
+static struct ast_frame *null_read(struct ast_channel *chan)
+{
+       /* Hangup channel. */
+       return NULL;
+}
+
+static struct ast_frame *null_exception(struct ast_channel *chan)
+{
+       /* Hangup channel. */
+       return NULL;
+}
+
+static int null_write(struct ast_channel *chan, struct ast_frame *frame)
+{
+       /* Hangup channel. */
+       return -1;
+}
+
+static int null_fixup(struct ast_channel *oldchan, struct ast_channel *newchan)
+{
+       /* No problem fixing up the channel. */
+       return 0;
+}
+
+static int null_hangup(struct ast_channel *chan)
+{
+       chan->tech_pvt = NULL;
+       return 0;
+}
+
+static const struct ast_channel_tech null_tech = {
+       .type = "NULL",
+       .description = "NULL channel driver for atxfer",
+       .capabilities = -1,
+       .read = null_read,
+       .exception = null_exception,
+       .write = null_write,
+       .fixup = null_fixup,
+       .hangup = null_hangup,
+};
+#endif /* defined(ATXFER_NULL_TECH) */
+
+#if defined(ATXFER_NULL_TECH)
+/*!
+ * \internal
+ * \brief Set the channel technology to the NULL technology.
+ *
+ * \param chan Channel to change technology.
+ *
+ * \return Nothing
+ */
+static void set_null_chan_tech(struct ast_channel *chan)
+{
+       int idx;
+
+       ast_channel_lock(chan);
+
+       /* Hangup the channel's physical side */
+       if (chan->tech->hangup) {
+               chan->tech->hangup(chan);
+       }
+       if (chan->tech_pvt) {
+               ast_log(LOG_WARNING, "Channel '%s' may not have been hung up properly\n",
+                       chan->name);
+               ast_free(chan->tech_pvt);
+               chan->tech_pvt = NULL;
+       }
+
+       /* Install the NULL technology and wake up anyone waiting on it. */
+       chan->tech = &null_tech;
+       for (idx = 0; idx < AST_MAX_FDS; ++idx) {
+               switch (idx) {
+               case AST_ALERT_FD:
+               case AST_TIMING_FD:
+               case AST_GENERATOR_FD:
+                       /* Don't clear these fd's. */
+                       break;
+               default:
+                       chan->fds[idx] = -1;
+                       break;
+               }
+       }
+       ast_queue_frame(chan, &ast_null_frame);
+
+       ast_channel_unlock(chan);
+}
+#endif /* defined(ATXFER_NULL_TECH) */
+
+#if defined(ATXFER_NULL_TECH)
+/*!
+ * \internal
+ * \brief Set the channel name to something unique.
+ *
+ * \param chan Channel to change name.
+ *
+ * \return Nothing
+ */
+static void set_new_chan_name(struct ast_channel *chan)
+{
+       char *orig_name;
+       static int seq_num;
+
+       ast_channel_lock(chan);
+
+       orig_name = ast_strdupa(chan->name);
+       ast_string_field_build(chan, name, "%s<XFER_%x>", orig_name,
+               ast_atomic_fetchadd_int(&seq_num, +1));
+
+       ast_channel_unlock(chan);
+}
+#endif /* defined(ATXFER_NULL_TECH) */
+
 static void *dial_features_duplicate(void *data)
 {
        struct ast_dial_features *df = data, *df_copy;
@@ -267,7 +428,10 @@ static void check_goto_on_transfer(struct ast_channel *chan)
        }
 }
 
-static struct ast_channel *ast_feature_request_and_dial(struct ast_channel *caller, const char *type, int format, void *data, int timeout, int *outstate, const char *cid_num, const char *cid_name, const char *language);
+static struct ast_channel *feature_request_and_dial(struct ast_channel *caller,
+       struct ast_channel *transferee, const char *type,
+       int format, void *data, int timeout, int *outstate, const char *cid_num,
+       const char *cid_name, const char *language);
 
 static void *ast_bridge_call_thread(void *data)
 {
@@ -893,10 +1057,25 @@ static int check_compat(struct ast_channel *c, struct ast_channel *newchan)
        return 0;
 }
 
+/*!
+ * \brief Attended transfer
+ * \param chan transfered user
+ * \param peer person transfering call
+ * \param config
+ * \param code
+ * \param sense feature options
+ *
+ * \param data
+ * Get extension to transfer to, if you cannot generate channel (or find extension)
+ * return to host channel. After called channel answered wait for hangup of transferer,
+ * bridge call between transfer peer (taking them off hold) to attended transfer channel.
+ *
+ * \return -1 on failure
+*/
 static int builtin_atxfer(struct ast_channel *chan, struct ast_channel *peer, struct ast_bridge_config *config, char *code, int sense, void *data)
 {
-       struct ast_channel *transferer;
-       struct ast_channel *transferee;
+       struct ast_channel *transferer;/* Party B */
+       struct ast_channel *transferee;/* Party A */
        const char *transferer_real_context;
        char xferto[256] = "";
        int res;
@@ -905,7 +1084,6 @@ static int builtin_atxfer(struct ast_channel *chan, struct ast_channel *peer, st
        struct ast_channel *xferchan;
        struct ast_bridge_thread_obj *tobj;
        struct ast_bridge_config bconfig;
-       struct ast_frame *f;
        int l;
        struct ast_datastore *features_datastore;
        struct ast_dial_features *dialfeatures = NULL;
@@ -914,40 +1092,37 @@ static int builtin_atxfer(struct ast_channel *chan, struct ast_channel *peer, st
                ast_log(LOG_DEBUG, "Executing Attended Transfer %s, %s (sense=%d) \n", chan->name, peer->name, sense);
        set_peers(&transferer, &transferee, peer, chan, sense);
        transferer_real_context = real_ctx(transferer, transferee);
-       /* Start autoservice on chan while we talk to the originator */
+
+       /* Start autoservice on transferee while we talk to the transferer */
        ast_autoservice_start(transferee);
-       ast_autoservice_ignore(transferee, AST_FRAME_DTMF_END);
        ast_indicate(transferee, AST_CONTROL_HOLD);
 
        /* Transfer */
        res = ast_stream_and_wait(transferer, "pbx-transfer", transferer->language, AST_DIGIT_ANY);
        if (res < 0) {
                finishup(transferee);
-               return res;
+               return -1;
        }
        if (res > 0) /* If they've typed a digit already, handle it */
                xferto[0] = (char) res;
 
        /* this is specific of atxfer */
        res = ast_app_dtget(transferer, transferer_real_context, xferto, sizeof(xferto), 100, transferdigittimeout);
-        if (res < 0) {  /* hangup, would be 0 for invalid and 1 for valid */
-                finishup(transferee);
-                return res;
-        }
-       if (res == 0) {
-               ast_log(LOG_WARNING, "Did not read data.\n");
+       if (res < 0) {  /* hangup or error, (would be 0 for invalid and 1 for valid) */
                finishup(transferee);
-               if (ast_stream_and_wait(transferer, "beeperr", transferer->language, ""))
-                       return -1;
-               return FEATURE_RETURN_SUCCESS;
+               return -1;
        }
-
-       /* valid extension, res == 1 */
-       if (!ast_exists_extension(transferer, transferer_real_context, xferto, 1, transferer->cid.cid_num)) {
-               ast_log(LOG_WARNING, "Extension %s does not exist in context %s\n",xferto,transferer_real_context);
+       l = strlen(xferto);
+       if (res == 0) {
+               if (l) {
+                       ast_log(LOG_WARNING, "Extension '%s' does not exist in context '%s'\n",
+                               xferto, transferer_real_context);
+               } else {
+                       /* Does anyone care about this case? */
+                       ast_log(LOG_WARNING, "No digits dialed for atxfer.\n");
+               }
+               ast_stream_and_wait(transferer, "pbx-invalid", transferer->language, "");
                finishup(transferee);
-               if (ast_stream_and_wait(transferer, "beeperr", transferer->language, ""))
-                       return -1;
                return FEATURE_RETURN_SUCCESS;
        }
 
@@ -958,27 +1133,63 @@ static int builtin_atxfer(struct ast_channel *chan, struct ast_channel *peer, st
                return builtin_parkcall(chan, peer, config, code, sense, data);
        }
 
-       l = strlen(xferto);
-       snprintf(xferto + l, sizeof(xferto) - l, "@%s", transferer_real_context);       /* append context */
-       newchan = ast_feature_request_and_dial(transferer, "Local", ast_best_codec(transferer->nativeformats),
-               xferto, atxfernoanswertimeout, &outstate, transferer->cid.cid_num, transferer->cid.cid_name, transferer->language);
-       ast_indicate(transferer, -1);
-       if (!newchan) {
-               finishup(transferee);
-               /* any reason besides user requested cancel and busy triggers the failed sound */
-               if (outstate != AST_CONTROL_UNHOLD && outstate != AST_CONTROL_BUSY &&
-                               ast_stream_and_wait(transferer, xferfailsound, transferer->language, ""))
-                       return -1;
-               return FEATURE_RETURN_SUCCESS;
+       /* Append context to dialed transfer number. */
+       snprintf(xferto + l, sizeof(xferto) - l, "@%s/n", transferer_real_context);
+
+       /* Stop autoservice so we can monitor all parties involved in the transfer. */
+       if (ast_autoservice_stop(transferee) < 0) {
+               ast_indicate(transferee, AST_CONTROL_UNHOLD);
+               return -1;
+       }
+
+       /* Dial party C */
+       newchan = feature_request_and_dial(transferer, transferee, "Local",
+               ast_best_codec(transferer->nativeformats), xferto, atxfernoanswertimeout,
+               &outstate, transferer->cid.cid_num, transferer->cid.cid_name,
+               transferer->language);
+       if (option_debug) {
+               ast_log(LOG_DEBUG, "Dial party C result: newchan:%d, outstate:%d\n", !!newchan, outstate);
        }
 
        if (!ast_check_hangup(transferer)) {
                int hangup_dont = 0;
 
+               /* Transferer (party B) is up */
+               if (option_debug) {
+                       ast_log(LOG_DEBUG, "Actually doing an attended transfer.\n");
+               }
+
+               /* Start autoservice on transferee while the transferer deals with party C. */
+               ast_autoservice_start(transferee);
+
+               ast_indicate(transferer, -1);
+               if (!newchan) {
+                       /* any reason besides user requested cancel and busy triggers the failed sound */
+                       switch (outstate) {
+                       case AST_CONTROL_UNHOLD:/* Caller requested cancel or party C answer timeout. */
+                       case AST_CONTROL_BUSY:
+                       case AST_CONTROL_CONGESTION:
+                               if (ast_stream_and_wait(transferer, xfersound, transferer->language, "")) {
+                                       ast_log(LOG_WARNING, "Failed to play transfer sound!\n");
+                               }
+                               break;
+                       default:
+                               if (ast_stream_and_wait(transferer, xferfailsound, transferer->language, "")) {
+                                       ast_log(LOG_WARNING, "Failed to play transfer failed sound!\n");
+                               }
+                               break;
+                       }
+                       finishup(transferee);
+                       return FEATURE_RETURN_SUCCESS;
+               }
+
                if (check_compat(transferer, newchan)) {
+                       if (ast_stream_and_wait(transferer, xferfailsound, transferer->language, "")) {
+                               ast_log(LOG_WARNING, "Failed to play transfer failed sound!\n");
+                       }
                        /* we do mean transferee here, NOT transferer */
                        finishup(transferee);
-                       return -1;
+                       return FEATURE_RETURN_SUCCESS;
                }
                memset(&bconfig,0,sizeof(struct ast_bridge_config));
                ast_set_flag(&(bconfig.features_caller), AST_FEATURE_DISCONNECT);
@@ -990,94 +1201,99 @@ static int builtin_atxfer(struct ast_channel *chan, struct ast_channel *peer, st
                if (ast_test_flag(chan, AST_FLAG_BRIDGE_HANGUP_DONT)) {
                        hangup_dont = 1;
                }
-               res = ast_bridge_call(transferer, newchan, &bconfig);
+               /* Let party B and party C talk as long as they want. */
+               ast_bridge_call(transferer, newchan, &bconfig);
                if (hangup_dont) {
                        ast_set_flag(chan, AST_FLAG_BRIDGE_HANGUP_DONT);
                }
 
-               if (newchan->_softhangup || !transferer->_softhangup) {
+               if (ast_check_hangup(newchan) || !ast_check_hangup(transferer)) {
                        ast_hangup(newchan);
-                       if (ast_stream_and_wait(transferer, xfersound, transferer->language, ""))
+                       if (ast_stream_and_wait(transferer, xfersound, transferer->language, "")) {
                                ast_log(LOG_WARNING, "Failed to play transfer sound!\n");
+                       }
                        finishup(transferee);
-                       transferer->_softhangup = 0;
                        return FEATURE_RETURN_SUCCESS;
                }
-       } else {
-               ast_log(LOG_DEBUG, "transferer hangup; outstate = %d\n", outstate);
-               switch (outstate) {
-               case AST_CONTROL_RINGING:
-               {
-                       int connected = 0;
-
-                       ast_indicate(transferee, AST_CONTROL_UNHOLD);
-                       ast_indicate(transferee, AST_CONTROL_RINGING);
-                       while (!connected && (ast_waitfor(newchan, -1) >= 0)) {
-                               if ((f = ast_read(newchan)) == NULL) {
-                                       break;
-                               }
-                               if (f->frametype == AST_FRAME_CONTROL && f->subclass == AST_CONTROL_ANSWER) {
-                                       connected = 1;
-                               }
-                               ast_frfree(f);
-                       }
-                       if (!connected) {
-                               ast_hangup(newchan);
-                               finishup(transferee);
-                               return -1;
-                       }
-                       /* fall through */
-               }
-               case AST_CONTROL_ANSWER:
-                       ast_log(LOG_DEBUG, "transferer hangup; callee answered\n");
-                       break;
 
-               default:
-                       ast_hangup(newchan);
+               /* Transferer (party B) is confirmed hung up at this point. */
+               if (check_compat(transferee, newchan)) {
                        finishup(transferee);
-                       return FEATURE_RETURN_SUCCESS;
+                       return -1;
                }
-       }
 
-       if (check_compat(transferee, newchan)) {
-               finishup(transferee);
-               return -1;
-       }
+               ast_indicate(transferee, AST_CONTROL_UNHOLD);
+               if ((ast_autoservice_stop(transferee) < 0)
+                       || (ast_waitfordigit(transferee, 100) < 0)
+                       || (ast_waitfordigit(newchan, 100) < 0)
+                       || ast_check_hangup(transferee)
+                       || ast_check_hangup(newchan)) {
+                       ast_hangup(newchan);
+                       return -1;
+               }
+       } else if (!ast_check_hangup(transferee)) {
+               /* Transferer (party B) has hung up at this point.  Doing blonde transfer. */
+               if (option_debug) {
+                       ast_log(LOG_DEBUG, "Actually doing a blonde transfer.\n");
+               }
 
-       ast_indicate(transferee, AST_CONTROL_UNHOLD);
+               if (!newchan) {
+                       /* No party C. */
+                       return -1;
+               }
 
-       if ((ast_autoservice_stop(transferee) < 0)
-          || (ast_waitfordigit(transferee, 100) < 0)
-          || (ast_waitfordigit(newchan, 100) < 0) 
-          || ast_check_hangup(transferee) 
-          || ast_check_hangup(newchan)) {
-               ast_hangup(newchan);
+               /* newchan is up, we should prepare transferee and bridge them */
+               if (ast_check_hangup(newchan)) {
+                       ast_hangup(newchan);
+                       return -1;
+               }
+               if (check_compat(transferee, newchan)) {
+                       return -1;
+               }
+       } else {
+               /*
+                * Both the transferer and transferee have hungup.  If newchan
+                * is up, hang it up as it has no one to talk to.
+                */
+               if (option_debug) {
+                       ast_log(LOG_DEBUG, "Everyone is hungup.\n");
+               }
+               if (newchan) {
+                       ast_hangup(newchan);
+               }
                return -1;
        }
 
+       /* Initiate the channel transfer of party A to party C. */
+
        xferchan = ast_channel_alloc(0, AST_STATE_DOWN, 0, 0, "", "", "", 0, "Transfered/%s", transferee->name);
        if (!xferchan) {
                ast_hangup(newchan);
                return -1;
        }
+
+       /* Give party A a momentary ringback tone during transfer. */
+       xferchan->visible_indication = AST_CONTROL_RINGING;
+
        /* Make formats okay */
-       xferchan->visible_indication = transferer->visible_indication;
        xferchan->readformat = transferee->readformat;
        xferchan->writeformat = transferee->writeformat;
+
        ast_channel_masquerade(xferchan, transferee);
        ast_explicit_goto(xferchan, transferee->context, transferee->exten, transferee->priority);
        xferchan->_state = AST_STATE_UP;
-       ast_clear_flag(xferchan, AST_FLAGS_ALL);        
-       xferchan->_softhangup = 0;
+       ast_clear_flag(xferchan, AST_FLAGS_ALL);
 
-       if ((f = ast_read(xferchan)))
-               ast_frfree(f);
+       /* Do the masquerade manually to make sure that is is completed. */
+       ast_channel_lock(xferchan);
+       if (xferchan->masq) {
+               ast_do_masquerade(xferchan);
+       }
+       ast_channel_unlock(xferchan);
 
        newchan->_state = AST_STATE_UP;
-       ast_clear_flag(newchan, AST_FLAGS_ALL); 
-       newchan->_softhangup = 0;
-
-       tobj = ast_calloc(1, sizeof(struct ast_bridge_thread_obj));
+       ast_clear_flag(newchan, AST_FLAGS_ALL);
+       tobj = ast_calloc(1, sizeof(*tobj));
        if (!tobj) {
                ast_hangup(xferchan);
                ast_hangup(newchan);
@@ -1094,6 +1310,7 @@ static int builtin_atxfer(struct ast_channel *chan, struct ast_channel *peer, st
                /* newchan should always be the callee and shows up as callee in dialfeatures, but for some reason
                   I don't currently understand, the abilities of newchan seem to be stored on the caller side */
                ast_copy_flags(&(config->features_callee), &(dialfeatures->features_caller), AST_FLAGS_ALL);
+               dialfeatures = NULL;
        }
 
        ast_channel_lock(xferchan);
@@ -1117,7 +1334,7 @@ static int builtin_atxfer(struct ast_channel *chan, struct ast_channel *peer, st
        if (ast_stream_and_wait(newchan, xfersound, newchan->language, ""))
                ast_log(LOG_WARNING, "Failed to play transfer sound!\n");
        ast_bridge_call_thread_launch(tobj);
-       return -1;      /* XXX meaning the channel is bridged ? */
+       return -1;/* The transferee is masqueraded and the original bridged channels can be hungup. */
 }
 
 
@@ -1450,168 +1667,293 @@ static void set_config_flags(struct ast_channel *chan, struct ast_channel *peer,
        }
 }
 
-/*! \todo XXX Check - this is very similar to the code in channel.c */
-static struct ast_channel *ast_feature_request_and_dial(struct ast_channel *caller, const char *type, int format, void *data, int timeout, int *outstate, const char *cid_num, const char *cid_name, const char *language)
+/*!
+ * \internal
+ * \brief Get feature and dial.
+ *
+ * \param caller Channel to represent as the calling channel for the dialed channel.
+ * \param transferee Channel that the dialed channel will be transferred to.
+ * \param type Channel technology type to dial.
+ * \param format Codec formats for dialed channel.
+ * \param data Dialed channel extra parameters for ast_request() and ast_call().
+ * \param timeout Time limit for dialed channel to answer in ms. Must be greater than zero.
+ * \param outstate Status of dialed channel if unsuccessful.
+ * \param cid_num CallerID number to give dialed channel.
+ * \param cid_name CallerID name to give dialed channel.
+ * \param language Language of the caller.
+ *
+ * \note
+ * outstate can be:
+ * 0, AST_CONTROL_BUSY, AST_CONTROL_CONGESTION,
+ * AST_CONTROL_ANSWER, or AST_CONTROL_UNHOLD.  If
+ * AST_CONTROL_UNHOLD then the caller channel cancelled the
+ * transfer or the dialed channel did not answer before the
+ * timeout.
+ *
+ * \details
+ * Request channel, set channel variables, initiate call,
+ * check if they want to disconnect, go into loop, check if timeout has elapsed,
+ * check if person to be transfered hung up, check for answer break loop,
+ * set cdr return channel.
+ *
+ * \retval Channel Connected channel for transfer.
+ * \retval NULL on failure to get third party connected.
+ *
+ * \note This is similar to __ast_request_and_dial() in channel.c
+ */
+static struct ast_channel *feature_request_and_dial(struct ast_channel *caller,
+       struct ast_channel *transferee, const char *type,
+       int format, void *data, int timeout, int *outstate, const char *cid_num,
+       const char *cid_name, const char *language)
 {
        int state = 0;
        int cause = 0;
        int to;
+       int caller_hungup;
+       int transferee_hungup;
        struct ast_channel *chan;
-       struct ast_channel *monitor_chans[2];
+       struct ast_channel *monitor_chans[3];
        struct ast_channel *active_channel;
-       int res = 0, ready = 0;
-       
-       if ((chan = ast_request(type, format, data, &cause))) {
-               ast_set_callerid(chan, cid_num, cid_name, cid_num);
-               ast_string_field_set(chan, language, language);
-               ast_channel_inherit_variables(caller, chan);    
-               pbx_builtin_setvar_helper(chan, "TRANSFERERNAME", caller->name);
-                       
-               if (!ast_call(chan, data, timeout)) {
-                       struct timeval started;
-                       int x, len = 0;
-                       char *disconnect_code = NULL, *dialed_code = NULL;
-
-                       ast_indicate(caller, AST_CONTROL_RINGING);
-                       /* support dialing of the featuremap disconnect code while performing an attended tranfer */
-                       ast_rwlock_rdlock(&features_lock);
-                       for (x = 0; x < FEATURES_COUNT; x++) {
-                               if (strcasecmp(builtin_features[x].sname, "disconnect"))
-                                       continue;
+       int ready = 0;
+       struct timeval started;
+       int x, len = 0;
+       char *disconnect_code = NULL, *dialed_code = NULL;
+       struct ast_frame *f;
+       AST_LIST_HEAD_NOLOCK(, ast_frame) deferred_frames;
 
-                               disconnect_code = builtin_features[x].exten;
-                               len = strlen(disconnect_code) + 1;
-                               dialed_code = alloca(len);
-                               memset(dialed_code, 0, len);
-                               break;
-                       }
-                       ast_rwlock_unlock(&features_lock);
-                       x = 0;
-                       started = ast_tvnow();
-                       to = timeout;
-                       while (!ast_check_hangup(caller) && timeout && (chan->_state != AST_STATE_UP)) {
-                               struct ast_frame *f = NULL;
-
-                               monitor_chans[0] = caller;
-                               monitor_chans[1] = chan;
-                               active_channel = ast_waitfor_n(monitor_chans, 2, &to);
-
-                               /* see if the timeout has been violated */
-                               if(ast_tvdiff_ms(ast_tvnow(), started) > timeout) {
-                                       state = AST_CONTROL_UNHOLD;
-                                       ast_log(LOG_NOTICE, "We exceeded our AT-timeout\n");
-                                       break; /*doh! timeout*/
-                               }
+       caller_hungup = ast_check_hangup(caller);
 
-                               if (!active_channel)
-                                       continue;
+       if (!(chan = ast_request(type, format, data, &cause))) {
+               ast_log(LOG_NOTICE, "Unable to request channel %s/%s\n", type, (char *)data);
+               switch (cause) {
+               case AST_CAUSE_BUSY:
+                       state = AST_CONTROL_BUSY;
+                       break;
+               case AST_CAUSE_CONGESTION:
+                       state = AST_CONTROL_CONGESTION;
+                       break;
+               default:
+                       state = 0;
+                       break;
+               }
+               goto done;
+       }
 
-                               if (chan && (chan == active_channel)) {
-                                       if (!ast_strlen_zero(chan->call_forward)) {
-                                               if (!(chan = ast_call_forward(caller, chan, NULL, format, NULL, outstate))) {
-                                                       return NULL;
-                                               }
-                                               continue;
-                                       }
-                                       f = ast_read(chan);
-                                       if (f == NULL) { /*doh! where'd he go?*/
-                                               state = AST_CONTROL_HANGUP;
-                                               res = 0;
-                                               break;
-                                       }
-                                       
-                                       if (f->frametype == AST_FRAME_CONTROL || f->frametype == AST_FRAME_DTMF || f->frametype == AST_FRAME_TEXT) {
-                                               if (f->subclass == AST_CONTROL_RINGING) {
-                                                       state = f->subclass;
-                                                       if (option_verbose > 2)
-                                                               ast_verbose( VERBOSE_PREFIX_3 "%s is ringing\n", chan->name);
-                                                       ast_indicate(caller, AST_CONTROL_RINGING);
-                                               } else if ((f->subclass == AST_CONTROL_BUSY) || (f->subclass == AST_CONTROL_CONGESTION)) {
-                                                       state = f->subclass;
-                                                       if (option_verbose > 2)
-                                                               ast_verbose( VERBOSE_PREFIX_3 "%s is busy\n", chan->name);
-                                                       ast_indicate(caller, AST_CONTROL_BUSY);
-                                                       ast_frfree(f);
-                                                       f = NULL;
-                                                       break;
-                                               } else if (f->subclass == AST_CONTROL_ANSWER) {
-                                                       /* This is what we are hoping for */
-                                                       state = f->subclass;
-                                                       ast_frfree(f);
-                                                       f = NULL;
-                                                       ready=1;
-                                                       break;
-                                               } else if (f->subclass != -1 && f->subclass != AST_CONTROL_PROGRESS) {
-                                                       ast_log(LOG_NOTICE, "Don't know what to do about control frame: %d\n", f->subclass);
-                                               }
-                                               /* else who cares */
-                                       } else if (f->frametype == AST_FRAME_VOICE || f->frametype == AST_FRAME_VIDEO) {
-                                               ast_write(caller, f);
-                                       }
+       ast_set_callerid(chan, cid_num, cid_name, cid_num);
+       ast_string_field_set(chan, language, language);
+       ast_channel_inherit_variables(caller, chan);
+       pbx_builtin_setvar_helper(chan, "TRANSFERERNAME", caller->name);
 
-                               } else if (caller && (active_channel == caller)) {
-                                       f = ast_read(caller);
-                                       if (f == NULL) { /*doh! where'd he go?*/
-                                               if (caller->_softhangup && !chan->_softhangup) {
-                                                       /* make this a blind transfer */
-                                                       ready = 1;
-                                                       break;
-                                               }
-                                               state = AST_CONTROL_HANGUP;
-                                               res = 0;
-                                               break;
-                                       }
-                                       
-                                       if (f->frametype == AST_FRAME_DTMF) {
-                                               dialed_code[x++] = f->subclass;
-                                               dialed_code[x] = '\0';
-                                               if (strlen(dialed_code) == len) {
-                                                       x = 0;
-                                               } else if (x && strncmp(dialed_code, disconnect_code, x)) {
-                                                       x = 0;
-                                                       dialed_code[x] = '\0';
-                                               }
-                                               if (*dialed_code && !strcmp(dialed_code, disconnect_code)) {
-                                                       /* Caller Canceled the call */
-                                                       state = AST_CONTROL_UNHOLD;
-                                                       ast_frfree(f);
-                                                       f = NULL;
-                                                       break;
-                                               }
-                                       } else if (f->frametype == AST_FRAME_VOICE || f->frametype == AST_FRAME_VIDEO) {
-                                               ast_write(chan, f);
-                                       }
-                               }
-                               if (f)
-                                       ast_frfree(f);
-                       } /* end while */
-               } else
-                       ast_log(LOG_NOTICE, "Unable to call channel %s/%s\n", type, (char *)data);
-       } else {
-               ast_log(LOG_NOTICE, "Unable to request channel %s/%s\n", type, (char *)data);
-               switch(cause) {
+       if (ast_call(chan, data, timeout)) {
+               ast_log(LOG_NOTICE, "Unable to call channel %s/%s\n", type, (char *)data);
+               switch (chan->hangupcause) {
                case AST_CAUSE_BUSY:
                        state = AST_CONTROL_BUSY;
                        break;
                case AST_CAUSE_CONGESTION:
                        state = AST_CONTROL_CONGESTION;
                        break;
+               default:
+                       state = 0;
+                       break;
                }
+               goto done;
        }
-       
+
+       /* support dialing of the featuremap disconnect code while performing an attended tranfer */
+       ast_rwlock_rdlock(&features_lock);
+       for (x = 0; x < FEATURES_COUNT; x++) {
+               if (strcasecmp(builtin_features[x].sname, "disconnect"))
+                       continue;
+
+               disconnect_code = builtin_features[x].exten;
+               len = strlen(disconnect_code) + 1;
+               dialed_code = alloca(len);
+               memset(dialed_code, 0, len);
+               break;
+       }
+       ast_rwlock_unlock(&features_lock);
+       x = 0;
+       started = ast_tvnow();
+       to = timeout;
+       AST_LIST_HEAD_INIT_NOLOCK(&deferred_frames);
+
+       if (caller_hungup) {
+               /* Convert to a blonde transfer */
+               ast_indicate(transferee, AST_CONTROL_UNHOLD);
+               ast_indicate(transferee, AST_CONTROL_RINGING);
+       }
+
+       transferee_hungup = 0;
+       while (!ast_check_hangup(transferee) && (chan->_state != AST_STATE_UP)) {
+               int num_chans = 0;
+
+               monitor_chans[num_chans++] = transferee;
+               monitor_chans[num_chans++] = chan;
+               if (!caller_hungup) {
+                       if (ast_check_hangup(caller)) {
+                               caller_hungup = 1;
+
+#if defined(ATXFER_NULL_TECH)
+                               /* Change caller's name to ensure that it will remain unique. */
+                               set_new_chan_name(caller);
+
+                               /*
+                                * Get rid of caller's physical technology so it is free for
+                                * other calls.
+                                */
+                               set_null_chan_tech(caller);
+#endif /* defined(ATXFER_NULL_TECH) */
+
+                               /* Convert to a blonde transfer */
+                               ast_indicate(transferee, AST_CONTROL_UNHOLD);
+                               ast_indicate(transferee, AST_CONTROL_RINGING);
+                               started = ast_tvnow();
+                               to = timeout;
+                       } else {
+                               /* caller is not hungup so monitor it. */
+                               monitor_chans[num_chans++] = caller;
+                       }
+               }
+
+               /* see if the timeout has been violated */
+               if (ast_tvdiff_ms(ast_tvnow(), started) > timeout) {
+                       state = AST_CONTROL_UNHOLD;
+                       ast_log(LOG_NOTICE, "We exceeded our AT-timeout for %s\n", chan->name);
+                       break; /*doh! timeout*/
+               }
+
+               active_channel = ast_waitfor_n(monitor_chans, num_chans, &to);
+               if (!active_channel)
+                       continue;
+
+               f = NULL;
+               if (transferee == active_channel) {
+                       struct ast_frame *dup_f;
+
+                       f = ast_read(transferee);
+                       if (f == NULL) { /*doh! where'd he go?*/
+                               transferee_hungup = 1;
+                               state = 0;
+                               break;
+                       }
+                       if (ast_is_deferrable_frame(f)) {
+                               dup_f = ast_frisolate(f);
+                               if (dup_f) {
+                                       if (dup_f == f) {
+                                               f = NULL;
+                                       }
+                                       AST_LIST_INSERT_HEAD(&deferred_frames, dup_f, frame_list);
+                               }
+                       }
+               } else if (chan == active_channel) {
+                       if (!ast_strlen_zero(chan->call_forward)) {
+                               state = 0;
+                               chan = ast_call_forward(caller, chan, NULL, format, NULL, &state);
+                               if (!chan) {
+                                       break;
+                               }
+                               continue;
+                       }
+                       f = ast_read(chan);
+                       if (f == NULL) { /*doh! where'd he go?*/
+                               switch (chan->hangupcause) {
+                               case AST_CAUSE_BUSY:
+                                       state = AST_CONTROL_BUSY;
+                                       break;
+                               case AST_CAUSE_CONGESTION:
+                                       state = AST_CONTROL_CONGESTION;
+                                       break;
+                               default:
+                                       state = 0;
+                                       break;
+                               }
+                               break;
+                       }
+
+                       if (f->frametype == AST_FRAME_CONTROL) {
+                               if (f->subclass == AST_CONTROL_RINGING) {
+                                       if (option_verbose > 2)
+                                               ast_verbose(VERBOSE_PREFIX_3 "%s is ringing\n", chan->name);
+                                       ast_indicate(caller, AST_CONTROL_RINGING);
+                               } else if (f->subclass == AST_CONTROL_BUSY) {
+                                       state = f->subclass;
+                                       if (option_verbose > 2)
+                                               ast_verbose(VERBOSE_PREFIX_3 "%s is busy\n", chan->name);
+                                       ast_indicate(caller, AST_CONTROL_BUSY);
+                                       ast_frfree(f);
+                                       break;
+                               } else if (f->subclass == AST_CONTROL_CONGESTION) {
+                                       state = f->subclass;
+                                       if (option_verbose > 2)
+                                               ast_verbose(VERBOSE_PREFIX_3 "%s is congested\n", chan->name);
+                                       ast_indicate(caller, AST_CONTROL_CONGESTION);
+                                       ast_frfree(f);
+                                       break;
+                               } else if (f->subclass == AST_CONTROL_ANSWER) {
+                                       /* This is what we are hoping for */
+                                       state = f->subclass;
+                                       ast_frfree(f);
+                                       ready=1;
+                                       break;
+                               } else if (f->subclass != -1 && f->subclass != AST_CONTROL_PROGRESS) {
+                                       ast_log(LOG_NOTICE, "Don't know what to do about control frame: %d\n", f->subclass);
+                               }
+                               /* else who cares */
+                       } else if (f->frametype == AST_FRAME_VOICE || f->frametype == AST_FRAME_VIDEO) {
+                               ast_write(caller, f);
+                       }
+               } else if (caller == active_channel) {
+                       f = ast_read(caller);
+                       if (f) {
+                               if (f->frametype == AST_FRAME_DTMF) {
+                                       dialed_code[x++] = f->subclass;
+                                       dialed_code[x] = '\0';
+                                       if (strlen(dialed_code) == len) {
+                                               x = 0;
+                                       } else if (x && strncmp(dialed_code, disconnect_code, x)) {
+                                               x = 0;
+                                               dialed_code[x] = '\0';
+                                       }
+                                       if (*dialed_code && !strcmp(dialed_code, disconnect_code)) {
+                                               /* Caller Canceled the call */
+                                               state = AST_CONTROL_UNHOLD;
+                                               ast_frfree(f);
+                                               break;
+                                       }
+                               } else if (f->frametype == AST_FRAME_VOICE || f->frametype == AST_FRAME_VIDEO) {
+                                       ast_write(chan, f);
+                               }
+                       }
+               }
+               if (f)
+                       ast_frfree(f);
+       } /* end while */
+
+       /*
+        * We need to free all the deferred frames, but we only need to
+        * queue the deferred frames if no hangup was received.
+        */
+       ast_channel_lock(transferee);
+       transferee_hungup = (transferee_hungup || ast_check_hangup(transferee));
+       while ((f = AST_LIST_REMOVE_HEAD(&deferred_frames, frame_list))) {
+               if (!transferee_hungup) {
+                       ast_queue_frame_head(transferee, f);
+               }
+               ast_frfree(f);
+       }
+       ast_channel_unlock(transferee);
+
+done:
        ast_indicate(caller, -1);
        if (chan && ready) {
-               if (chan->_state == AST_STATE_UP) 
+               if (chan->_state == AST_STATE_UP)
                        state = AST_CONTROL_ANSWER;
-               res = 0;
-       } else if(chan) {
-               res = -1;
+       } else if (chan) {
                ast_hangup(chan);
                chan = NULL;
-       } else {
-               res = -1;
        }
-       
+
        if (outstate)
                *outstate = state;