From a3b8feb9320f745f960fe8f7006183137f4969b1 Mon Sep 17 00:00:00 2001
From: Lennart Poettering <lennart@poettering.net>
Date: Mon, 2 Nov 2015 09:34:05 +0100
Subject: [PATCH] core: bump net.unix.max_dgram_qlen really early during boot

Only that way it actually has an effect on all our sockets, including
$NOTIFY_SOCKET.

(cherry picked from commit 19854865a877a3a4fa3d04550c15a99c0e1187ff)
Related: #1267707
---
 src/core/main.c  | 36 ++++++++++++++++++++++++++++++++++++
 src/shared/def.h |  3 +++
 2 files changed, 39 insertions(+)

diff --git a/src/core/main.c b/src/core/main.c
index 60ea36c..c9d8ce4 100644
--- a/src/core/main.c
+++ b/src/core/main.c
@@ -1198,6 +1198,7 @@ static int status_welcome(void) {
 
 static int write_container_id(void) {
         const char *c;
+        int r;
 
         c = getenv("container");
         if (isempty(c))
@@ -1206,6 +1207,40 @@ static int write_container_id(void) {
         return write_string_file("/run/systemd/container", c);
 }
 
+static int bump_unix_max_dgram_qlen(void) {
+        _cleanup_free_ char *qlen = NULL;
+        unsigned long v;
+        int r;
+
+        /* Let's bump the net.unix.max_dgram_qlen sysctl. The kernel
+         * default of 16 is simply too low. We set the value really
+         * really early during boot, so that it is actually applied to
+         * all our sockets, including the $NOTIFY_SOCKET one. */
+
+        r = read_one_line_file("/proc/sys/net/unix/max_dgram_qlen", &qlen);
+        if (r < 0)
+                return log_warning_errno(r, "Failed to read AF_UNIX datagram queue length, ignoring: %m");
+
+        r = safe_atolu(qlen, &v);
+        if (r < 0)
+                return log_warning_errno(r, "Failed to parse AF_UNIX datagram queue length, ignoring: %m");
+
+        if (v >= DEFAULT_UNIX_MAX_DGRAM_QLEN)
+                return 0;
+
+        free(qlen);
+        qlen = NULL;
+        if (asprintf(&qlen, "%lu\n", DEFAULT_UNIX_MAX_DGRAM_QLEN) < 0)
+                return log_oom();
+
+        r = write_string_file("/proc/sys/net/unix/max_dgram_qlen", qlen);
+        if (r < 0)
+                return log_full_errno(IN_SET(r, -EROFS, -EPERM, -EACCES) ? LOG_DEBUG : LOG_WARNING, r,
+                                      "Failed to bump AF_UNIX datagram queue length, ignoring: %m");
+
+        return 1;
+}
+
 int main(int argc, char *argv[]) {
         Manager *m = NULL;
         int r, retval = EXIT_FAILURE;
@@ -1571,6 +1606,7 @@ int main(int argc, char *argv[]) {
                 hostname_setup();
                 machine_id_setup(NULL);
                 loopback_setup();
+                bump_unix_max_dgram_qlen();
 
                 test_mtab();
                 test_usr();
diff --git a/src/shared/def.h b/src/shared/def.h
index a3d9fcf..76daf01 100644
--- a/src/shared/def.h
+++ b/src/shared/def.h
@@ -35,6 +35,9 @@
  * the watchdog pings will keep the loop busy. */
 #define DEFAULT_EXIT_USEC (30*USEC_PER_SEC)
 
+/* The default value for the net.unix.max_dgram_qlen sysctl */
+#define DEFAULT_UNIX_MAX_DGRAM_QLEN 512UL
+
 #define SYSTEMD_CGROUP_CONTROLLER "name=systemd"
 
 #define SIGNALS_CRASH_HANDLER SIGSEGV,SIGILL,SIGFPE,SIGBUS,SIGQUIT,SIGABRT