From c1d06d9501f26f7c16fe4136b6b8dcb7f473a6d1 Mon Sep 17 00:00:00 2001
From: bt90 <btom1990@googlemail.com>
Date: Fri, 5 Mar 2021 08:08:29 +0100
Subject: [PATCH] build: Package sysctl configuration to raise UDP buffer size
 on Linux (#7417)

* Provide a sysctl config to raise max UDP buffer size

* Add sysctl config to deb

* Check if `deb-systemd-invoke` is available

Co-authored-by: otbutz <tbutz@optitool.de>
---
 build.go                           |  1 +
 etc/linux-sysctl/30-syncthing.conf |  3 +++
 etc/linux-sysctl/README.md         | 21 +++++++++++++++++++++
 script/post-upgrade                |  5 +++++
 4 files changed, 30 insertions(+)
 create mode 100644 etc/linux-sysctl/30-syncthing.conf
 create mode 100644 etc/linux-sysctl/README.md

diff --git a/build.go b/build.go
index 3b18c61e6..b38e1cd58 100644
--- a/build.go
+++ b/build.go
@@ -115,6 +115,7 @@ var targets = map[string]target{
 			{src: "etc/linux-systemd/system/syncthing@.service", dst: "deb/lib/systemd/system/syncthing@.service", perm: 0644},
 			{src: "etc/linux-systemd/system/syncthing-resume.service", dst: "deb/lib/systemd/system/syncthing-resume.service", perm: 0644},
 			{src: "etc/linux-systemd/user/syncthing.service", dst: "deb/usr/lib/systemd/user/syncthing.service", perm: 0644},
+			{src: "etc/linux-sysctl/30-syncthing.conf", dst: "deb/usr/lib/sysctl.d/30-syncthing.conf", perm: 0644},
 			{src: "etc/firewall-ufw/syncthing", dst: "deb/etc/ufw/applications.d/syncthing", perm: 0644},
 			{src: "etc/linux-desktop/syncthing-start.desktop", dst: "deb/usr/share/applications/syncthing-start.desktop", perm: 0644},
 			{src: "etc/linux-desktop/syncthing-ui.desktop", dst: "deb/usr/share/applications/syncthing-ui.desktop", perm: 0644},
diff --git a/etc/linux-sysctl/30-syncthing.conf b/etc/linux-sysctl/30-syncthing.conf
new file mode 100644
index 000000000..9c7787409
--- /dev/null
+++ b/etc/linux-sysctl/30-syncthing.conf
@@ -0,0 +1,3 @@
+# Increase maximum receive socket buffer size to 2MiB for QUIC connections
+# see https://github.com/lucas-clemente/quic-go/wiki/UDP-Receive-Buffer-Size
+net.core.rmem_max = 2097152
diff --git a/etc/linux-sysctl/README.md b/etc/linux-sysctl/README.md
new file mode 100644
index 000000000..0c0e06dfe
--- /dev/null
+++ b/etc/linux-sysctl/README.md
@@ -0,0 +1,21 @@
+sysctl configuration to raise UDP buffer size
+===================
+Installation
+-----------
+**Please note:** When you installed syncthing using the official deb package, you can skip the copying.
+
+Copy the file `30-syncthing.conf` to `/etc/sysctl.d/` (root permissions required).
+
+In a terminal run
+```
+sudo sysctl -q --system
+```
+to apply the sysctl changes.
+
+
+Verification
+----------
+You can verify that the new limit is active using
+```
+sysctl net.core.rmem_max
+```
diff --git a/script/post-upgrade b/script/post-upgrade
index 6be37d5bb..5fb8ad187 100644
--- a/script/post-upgrade
+++ b/script/post-upgrade
@@ -1,3 +1,8 @@
 #!/bin/sh
 
+if command -v deb-systemd-invoke > /dev/null; then
+	deb-systemd-invoke restart procps.service
+else
+	sysctl -q --system
+fi
 pkill -HUP -x syncthing || true