core_unreal: Fix T.38 faxing when using local channels.

After some changes to streams and topologies, receiving fax through
local channels stopped working. This change adds a stream topology with
a stream of type IMAGE to the local channel pair and allows fax to be
received.

ASTERISK-29035 #close

Change-Id: Id103cc5c9295295d8e68d5628e76220f8f17e9fb

diff --git a/include/asterisk/core_unreal.h b/include/asterisk/core_unreal.h
index a28d39d521cf4f44e2c6e6ccb33ac87ca2690f2a..c6e770bddf43cafd83b18f897d3f688bc53ae621 100644 (file)
--- a/include/asterisk/core_unreal.h
+++ b/include/asterisk/core_unreal.h
@@ -98,6 +98,8 @@ struct ast_unreal_pvt {
        /*! Base name of the unreal channels.  exten@context or other name. */
        char name[AST_MAX_EXTENSION + AST_MAX_CONTEXT + 2];
        struct ast_stream_topology *reqtopology;    /*!< Requested stream topology */
+       struct ast_stream_topology *owner_old_topology; /*!< Stored topology for owner side when we need to restore later (faxing) */
+       struct ast_stream_topology *chan_old_topology;  /*!< Stored topology for chan side when we need to restore later (faxing) */
 };
 
 #define AST_UNREAL_IS_OUTBOUND(a, b) ((a) == (b)->chan ? 1 : 0)

diff --git a/main/core_unreal.c b/main/core_unreal.c
index 16414e642e5ce68bd86ad4106f9f2b9d64760d51..5adc90d2f7e476133f85a9b298b588d65ee4efa0 100644 (file)
--- a/main/core_unreal.c
+++ b/main/core_unreal.c
@@ -623,6 +623,9 @@ int ast_unreal_indicate(struct ast_channel *ast, int condition, const void *data
 {
        struct ast_unreal_pvt *p = ast_channel_tech_pvt(ast);
        int res = 0;
+       struct ast_channel *chan = NULL;
+       struct ast_channel *owner = NULL;
+       const struct ast_control_t38_parameters *parameters;
 
        if (!p) {
                return -1;
@@ -677,6 +680,89 @@ int ast_unreal_indicate(struct ast_channel *ast, int condition, const void *data
                        res = unreal_colp_stream_topology_request_change(p, ast, data);
                }
                break;
+       case AST_CONTROL_T38_PARAMETERS:
+               parameters = data;
+               if (parameters->request_response == AST_T38_NEGOTIATED) {
+                       struct ast_stream *stream;
+                       struct ast_stream_topology *new_topology;
+
+                       stream = ast_stream_alloc("local_fax", AST_MEDIA_TYPE_IMAGE);
+                       if (!stream) {
+                               ast_log(LOG_ERROR, "Failed to allocate memory for stream.\n");
+                               res = -1;
+                               break;
+                       }
+                       new_topology = ast_stream_topology_alloc();
+                       if (!new_topology) {
+                               ast_log(LOG_ERROR, "Failed to allocate memory for stream topology.\n");
+                               ast_free(stream);
+                               res = -1;
+                               break;
+                       }
+                       ast_stream_topology_append_stream(new_topology, stream);
+
+                       /*
+                        * Lock both parts of the local channel so we can store their topologies and replace them with
+                        * one that has a stream with type IMAGE. We can just hold the reference on the unreal_pvt
+                        * structure and bump it, then steal the ref later when we are restoring the topology.
+                        *
+                        * We use ast_unreal_lock_all here because we don't know if the ;1 or ;2 side will get the
+                        * signaling and we need to be sure that the locking order is the same to prevent possible
+                        * deadlocks.
+                        */
+                       ast_unreal_lock_all(p, &chan, &owner);
+
+                       if (owner) {
+                               p->owner_old_topology = ao2_bump(ast_channel_get_stream_topology(owner));
+                               ast_channel_set_stream_topology(owner, new_topology);
+                       }
+
+                       if (chan) {
+                               p->chan_old_topology = ao2_bump(ast_channel_get_stream_topology(chan));
+
+                               /* Bump the ref for new_topology, since it will be used by both sides of the local channel */
+                               ao2_ref(new_topology, +1);
+                               ast_channel_set_stream_topology(chan, new_topology);
+                       }
+
+                       ao2_unlock(p);
+               } else if (parameters->request_response == AST_T38_TERMINATED) {
+                       /*
+                        * Lock both parts of the local channel so we can restore their topologies to the original.
+                        * The topology should be on the unreal_pvt structure, with a ref that we can steal. Same
+                        * conditions as above.
+                        */
+                       ast_unreal_lock_all(p, &chan, &owner);
+
+                       if (owner) {
+                               ast_channel_set_stream_topology(owner, p->owner_old_topology);
+                               p->owner_old_topology = NULL;
+                       }
+
+                       if (chan) {
+                               ast_channel_set_stream_topology(chan, p->chan_old_topology);
+                               p->chan_old_topology = NULL;
+                       }
+
+                       ao2_unlock(p);
+               }
+
+               /*
+                * We unlock ast_unreal_pvt in the above conditionals since there's no way to
+                * tell if it's been unlocked already or not when we get to this point, but
+                * if either of these are not NULL, we know that they are locked and need to
+                * unlock them.
+                */
+               if (owner) {
+                       ast_channel_unlock(owner);
+                       ast_channel_unref(owner);
+               }
+
+               if (chan) {
+                       ast_channel_unlock(chan);
+                       ast_channel_unref(chan);
+               }
+               /* Fall through for all T38 conditions */
        default:
                res = unreal_queue_indicate(p, ast, condition, data, datalen);
                break;
@@ -1012,6 +1098,8 @@ void ast_unreal_destructor(void *vdoomed)
        doomed->reqcap = NULL;
        ast_stream_topology_free(doomed->reqtopology);
        doomed->reqtopology = NULL;
+       ao2_cleanup(doomed->owner_old_topology);
+       ao2_cleanup(doomed->chan_old_topology);
 }
 
 struct ast_unreal_pvt *ast_unreal_alloc(size_t size, ao2_destructor_fn destructor, struct ast_format_cap *cap)