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From 4c6c21f92a8204abf031e42bb4949a0ecf039f7a Mon Sep 17 00:00:00 2001
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From: David Herrmann <dh.herrmann@gmail.com>
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Date: Wed, 11 Mar 2015 13:53:21 +0100
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Subject: [PATCH] bus-proxy: complain only once about queue overflows
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If the local peer does not dispatch its incoming queue, the bus-proxy will
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slowly fill its outgoing queue. Once its full, it will continously
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complain that it cannot forward its messages.
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As it turns out, pulseaudio does have an idle background dbus connection
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that is not integrated into any mainloop (and given that gdbus and
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libdbus1 both support background shared connections, PA is probably not
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the only example), therefore, the bus-proxy will loudly complain if it
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cannot forward NameOwnerChanged events once the queue is full.
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This commit makes the proxy track queue-state and complain only once the
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queue runs full, not if it is already full.
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A PA bug-report (and patch) has been filed, and other applications should
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be fixed similarly. Hence, lets keep the error message, instead of
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dropping it. It's unused resources we really want to get rid of, so
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silencing the message does not really help (which is actually what
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dbus-daemon does).
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(cherry picked from commit ec2c7b56599981a7d9e76b15c75af3e1af3e6f81)
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---
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 src/bus-proxyd/proxy.c | 16 ++++++++++++----
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 src/bus-proxyd/proxy.h |  1 +
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 2 files changed, 13 insertions(+), 4 deletions(-)
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diff --git a/src/bus-proxyd/proxy.c b/src/bus-proxyd/proxy.c
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index 3dea908f5..e13cf5e2e 100644
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--- a/src/bus-proxyd/proxy.c
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+++ b/src/bus-proxyd/proxy.c
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@@ -729,13 +729,21 @@ static int proxy_process_destination_to_local(Proxy *p) {
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                 /* Return the error to the client, if we can */
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                 synthetic_reply_method_errnof(m, r, "Failed to forward message we got from destination: %m");
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-                log_error_errno(r,
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-                         "Failed to forward message we got from destination: uid=" UID_FMT " gid=" GID_FMT" message=%s destination=%s path=%s interface=%s member=%s: %m",
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-                         p->local_creds.uid, p->local_creds.gid, bus_message_type_to_string(m->header->type),
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-                         strna(m->destination), strna(m->path), strna(m->interface), strna(m->member));
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+                if (r == -ENOBUFS) {
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+                        /* if local dbus1 peer does not dispatch its queue, warn only once */
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+                        if (!p->queue_overflow)
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+                                log_error("Dropped messages due to queue overflow of local peer (pid: "PID_FMT" uid: "UID_FMT")", p->local_creds.pid, p->local_creds.uid);
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+                        p->queue_overflow = true;
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+                } else
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+                        log_error_errno(r,
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+                                 "Failed to forward message we got from destination: uid=" UID_FMT " gid=" GID_FMT" message=%s destination=%s path=%s interface=%s member=%s: %m",
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+                                 p->local_creds.uid, p->local_creds.gid, bus_message_type_to_string(m->header->type),
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+                                 strna(m->destination), strna(m->path), strna(m->interface), strna(m->member));
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+
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                 return 1;
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         }
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+        p->queue_overflow = false;
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         return 1;
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 }
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diff --git a/src/bus-proxyd/proxy.h b/src/bus-proxyd/proxy.h
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index 913d47071..782c4e60b 100644
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--- a/src/bus-proxyd/proxy.h
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+++ b/src/bus-proxyd/proxy.h
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@@ -40,6 +40,7 @@ struct Proxy {
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         SharedPolicy *policy;
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         bool got_hello : 1;
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+        bool queue_overflow : 1;
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 };
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 int proxy_new(Proxy **out, int in_fd, int out_fd, const char *dest);