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From a3b8feb9320f745f960fe8f7006183137f4969b1 Mon Sep 17 00:00:00 2001
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From: Lennart Poettering <lennart@poettering.net>
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Date: Mon, 2 Nov 2015 09:34:05 +0100
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Subject: [PATCH] core: bump net.unix.max_dgram_qlen really early during boot
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Only that way it actually has an effect on all our sockets, including
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$NOTIFY_SOCKET.
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(cherry picked from commit 19854865a877a3a4fa3d04550c15a99c0e1187ff)
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Related: #1267707
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---
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 src/core/main.c  | 36 ++++++++++++++++++++++++++++++++++++
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 src/shared/def.h |  3 +++
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 2 files changed, 39 insertions(+)
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diff --git a/src/core/main.c b/src/core/main.c
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index 60ea36c3cb..c9d8ce4a40 100644
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--- a/src/core/main.c
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+++ b/src/core/main.c
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@@ -1198,6 +1198,7 @@ static int status_welcome(void) {
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 static int write_container_id(void) {
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         const char *c;
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+        int r;
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         c = getenv("container");
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         if (isempty(c))
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@@ -1206,6 +1207,40 @@ static int write_container_id(void) {
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         return write_string_file("/run/systemd/container", c);
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 }
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+static int bump_unix_max_dgram_qlen(void) {
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+        _cleanup_free_ char *qlen = NULL;
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+        unsigned long v;
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+        int r;
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+
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+        /* Let's bump the net.unix.max_dgram_qlen sysctl. The kernel
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+         * default of 16 is simply too low. We set the value really
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+         * really early during boot, so that it is actually applied to
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+         * all our sockets, including the $NOTIFY_SOCKET one. */
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+
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+        r = read_one_line_file("/proc/sys/net/unix/max_dgram_qlen", &qlen);
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+        if (r < 0)
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+                return log_warning_errno(r, "Failed to read AF_UNIX datagram queue length, ignoring: %m");
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+
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+        r = safe_atolu(qlen, &v);
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+        if (r < 0)
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+                return log_warning_errno(r, "Failed to parse AF_UNIX datagram queue length, ignoring: %m");
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+
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+        if (v >= DEFAULT_UNIX_MAX_DGRAM_QLEN)
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+                return 0;
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+
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+        free(qlen);
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+        qlen = NULL;
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+        if (asprintf(&qlen, "%lu\n", DEFAULT_UNIX_MAX_DGRAM_QLEN) < 0)
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+                return log_oom();
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+
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+        r = write_string_file("/proc/sys/net/unix/max_dgram_qlen", qlen);
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+        if (r < 0)
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+                return log_full_errno(IN_SET(r, -EROFS, -EPERM, -EACCES) ? LOG_DEBUG : LOG_WARNING, r,
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+                                      "Failed to bump AF_UNIX datagram queue length, ignoring: %m");
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+
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+        return 1;
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+}
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+
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 int main(int argc, char *argv[]) {
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         Manager *m = NULL;
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         int r, retval = EXIT_FAILURE;
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@@ -1571,6 +1606,7 @@ int main(int argc, char *argv[]) {
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                 hostname_setup();
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                 machine_id_setup(NULL);
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                 loopback_setup();
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+                bump_unix_max_dgram_qlen();
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                 test_mtab();
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                 test_usr();
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diff --git a/src/shared/def.h b/src/shared/def.h
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index a3d9fcf388..76daf012d7 100644
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--- a/src/shared/def.h
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+++ b/src/shared/def.h
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@@ -35,6 +35,9 @@
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  * the watchdog pings will keep the loop busy. */
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 #define DEFAULT_EXIT_USEC (30*USEC_PER_SEC)
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+/* The default value for the net.unix.max_dgram_qlen sysctl */
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+#define DEFAULT_UNIX_MAX_DGRAM_QLEN 512UL
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+
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 #define SYSTEMD_CGROUP_CONTROLLER "name=systemd"
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 #define SIGNALS_CRASH_HANDLER SIGSEGV,SIGILL,SIGFPE,SIGBUS,SIGQUIT,SIGABRT