client audio: Support memfd transport

Now that all layers in the stack support memfd blocks, add memfd
pools support for client context and audio playback data.

Use such memfd pools by default only if the server signals memfd
support in its connection negotiations.

Also add ability for clients to force-disable memfd transport
through the `enable-memfd=' client configuration option.

Signed-off-by: Ahmed S. Darwish <darwish.07@gmail.com>

1 files changed, 40 insertions, 4 deletions

diff --git a/src/pulse/context.c b/src/pulse/context.c
index ef3941604..69be5f497 100644
--- a/src/pulse/context.c
+++ b/src/pulse/context.c
@@ -173,7 +173,12 @@ pa_context *pa_context_new_with_proplist(pa_mainloop_api *mainloop, const char *
     c->srb_template.readfd = -1;
     c->srb_template.writefd = -1;
 
-    type = !c->conf->disable_shm ? PA_MEM_TYPE_SHARED_POSIX : PA_MEM_TYPE_PRIVATE;
+    c->memfd_on_local = (!c->conf->disable_memfd && pa_memfd_is_locally_supported());
+
+    type = (c->conf->disable_shm) ? PA_MEM_TYPE_PRIVATE :
+           ((!c->memfd_on_local) ?
+               PA_MEM_TYPE_SHARED_POSIX : PA_MEM_TYPE_SHARED_MEMFD);
+
     if (!(c->mempool = pa_mempool_new(type, c->conf->shm_size, true))) {
 
         if (!c->conf->disable_shm) {
@@ -482,6 +487,7 @@ static void setup_complete_callback(pa_pdispatch *pd, uint32_t command, uint32_t
         case PA_CONTEXT_AUTHORIZING: {
             pa_tagstruct *reply;
             bool shm_on_remote = false;
+            bool memfd_on_remote = false;
 
             if (pa_tagstruct_getu32(t, &c->version) < 0 ||
                 !pa_tagstruct_eof(t)) {
@@ -500,7 +506,15 @@ static void setup_complete_callback(pa_pdispatch *pd, uint32_t command, uint32_t
                not. */
             if (c->version >= 13) {
                 shm_on_remote = !!(c->version & 0x80000000U);
-                c->version &= 0x7FFFFFFFU;
+
+                /* Starting with protocol version 31, the second MSB of the version
+                 * tag reflects whether memfd is supported on the other PA end. */
+                if (c->version >= 31)
+                    memfd_on_remote = !!(c->version & 0x40000000U);
+
+                /* Reserve the two most-significant _bytes_ of the version tag
+                 * for flags. */
+                c->version &= 0x0000FFFFU;
             }
 
             pa_log_debug("Protocol version: remote %u, local %u", c->version, PA_PROTOCOL_VERSION);
@@ -526,6 +540,26 @@ static void setup_complete_callback(pa_pdispatch *pd, uint32_t command, uint32_t
             pa_log_debug("Negotiated SHM: %s", pa_yes_no(c->do_shm));
             pa_pstream_enable_shm(c->pstream, c->do_shm);
 
+            c->shm_type = PA_MEM_TYPE_PRIVATE;
+            if (c->do_shm) {
+                if (c->version >= 31 && memfd_on_remote && c->memfd_on_local) {
+                    const char *reason;
+
+                    pa_pstream_enable_memfd(c->pstream);
+                    if (pa_mempool_is_memfd_backed(c->mempool))
+                        if (pa_pstream_register_memfd_mempool(c->pstream, c->mempool, &reason))
+                            pa_log("Failed to regester memfd mempool. Reason: %s", reason);
+
+                    /* Even if memfd pool registration fails, the negotiated SHM type
+                     * shall remain memfd as both endpoints claim to support it. */
+                    c->shm_type = PA_MEM_TYPE_SHARED_MEMFD;
+                } else
+                    c->shm_type = PA_MEM_TYPE_SHARED_POSIX;
+            }
+
+            pa_log_debug("Memfd possible: %s", pa_yes_no(c->memfd_on_local));
+            pa_log_debug("Negotiated SHM type: %s", pa_mem_type_to_string(c->shm_type));
+
             reply = pa_tagstruct_command(c, PA_COMMAND_SET_CLIENT_NAME, &tag);
 
             if (c->version >= 13) {
@@ -593,8 +627,10 @@ static void setup_context(pa_context *c, pa_iochannel *io) {
     pa_log_debug("SHM possible: %s", pa_yes_no(c->do_shm));
 
     /* Starting with protocol version 13 we use the MSB of the version
-     * tag for informing the other side if we could do SHM or not */
-    pa_tagstruct_putu32(t, PA_PROTOCOL_VERSION | (c->do_shm ? 0x80000000U : 0));
+     * tag for informing the other side if we could do SHM or not.
+     * Starting from version 31, second MSB is used to flag memfd support. */
+    pa_tagstruct_putu32(t, PA_PROTOCOL_VERSION | (c->do_shm ? 0x80000000U : 0) |
+                        (c->memfd_on_local ? 0x40000000 : 0));
     pa_tagstruct_put_arbitrary(t, cookie, sizeof(cookie));
 
 #ifdef HAVE_CREDS