From e217ac503ecd5a2987061e2e1acc0229bcba01a9 Mon Sep 17 00:00:00 2001
From: Metalcape <dario.capecchi.m@gmail.com>
Date: Sun, 12 Mar 2023 19:40:35 +0100
Subject: [PATCH] Use modified knockd to set a cooldown on port 19132 (#2003)

---
 Dockerfile                       | 5 +++++
 build/alpine/install-packages.sh | 4 ++--
 build/ol/install-packages.sh     | 2 +-
 build/ubuntu/install-packages.sh | 6 +++---
 files/auto/autopause-daemon.sh   | 2 +-
 files/auto/knockd-config.cfg     | 1 +
 files/sudoers-mc                 | 2 +-
 scripts/start-autopause          | 5 +++++
 8 files changed, 19 insertions(+), 8 deletions(-)

diff --git a/Dockerfile b/Dockerfile
index 275cf21..fae23a0 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -52,6 +52,11 @@ RUN curl -fsSL ${MC_HELPER_BASE_URL}/mc-image-helper-${MC_HELPER_VERSION}.tgz \
   | tar -C /usr/share -zxf - \
   && ln -s /usr/share/mc-image-helper-${MC_HELPER_VERSION}/bin/mc-image-helper /usr/bin
 
+# Install modified knockd
+ADD https://github.com/Metalcape/knock/releases/download/0.8.1/knock-0.8.1-${TARGETARCH}${TARGETVARIANT}.tar.gz /tmp/knock.tar.gz
+RUN tar -xf /tmp/knock.tar.gz -C /usr/local/ && rm /tmp/knock.tar.gz
+RUN find /usr/lib -name 'libpcap.so.0.8' -execdir cp '{}' libpcap.so.1 \;
+
 VOLUME ["/data"]
 WORKDIR /data
 
diff --git a/build/alpine/install-packages.sh b/build/alpine/install-packages.sh
index fc2ffb8..4c11691 100755
--- a/build/alpine/install-packages.sh
+++ b/build/alpine/install-packages.sh
@@ -21,7 +21,7 @@ apk add --no-cache -U \
     rsync \
     nano \
     sudo \
-    knock \
     tar \
     zstd \
-    nfs-utils
\ No newline at end of file
+    nfs-utils \
+    libpcap
diff --git a/build/ol/install-packages.sh b/build/ol/install-packages.sh
index e8eeadf..eab5e56 100755
--- a/build/ol/install-packages.sh
+++ b/build/ol/install-packages.sh
@@ -33,6 +33,6 @@ dnf install -y ImageMagick \
   unzip \
   zstd \
   lbzip2 \
-  knock
+  libpcap
 
 bash /build/ol/install-gosu.sh
diff --git a/build/ubuntu/install-packages.sh b/build/ubuntu/install-packages.sh
index f5ed4d0..d7b8822 100755
--- a/build/ubuntu/install-packages.sh
+++ b/build/ubuntu/install-packages.sh
@@ -23,7 +23,7 @@ apt-get install -y \
   unzip \
   zstd \
   lbzip2 \
-  knockd \
-  nfs-common
+  nfs-common \
+  libpcap0.8
 
-apt-get clean
\ No newline at end of file
+apt-get clean
diff --git a/files/auto/autopause-daemon.sh b/files/auto/autopause-daemon.sh
index 1cbfcdb..be88403 100644
--- a/files/auto/autopause-daemon.sh
+++ b/files/auto/autopause-daemon.sh
@@ -45,7 +45,7 @@ if isTrue "${DEBUG_AUTOPAUSE}"; then
   knockdArgs+=(-D)
 fi
 
-sudo /usr/sbin/knockd "${knockdArgs[@]}"
+sudo /usr/local/sbin/knockd "${knockdArgs[@]}"
 if [ $? -ne 0 ] ; then
   logAutopause "Failed to start knockd daemon."
   logAutopause "Probable cause: Unable to attach to interface \"$AUTOPAUSE_KNOCK_INTERFACE\"."
diff --git a/files/auto/knockd-config.cfg b/files/auto/knockd-config.cfg
index 0334ad0..1c54cc4 100644
--- a/files/auto/knockd-config.cfg
+++ b/files/auto/knockd-config.cfg
@@ -13,3 +13,4 @@
 [unpauseMCServer-bedrock]
  sequence = 19132:udp
  command = /auto/resume.sh %IP%
+ seq_cooldown = 60
diff --git a/files/sudoers-mc b/files/sudoers-mc
index 2869c23..bc0c19c 100644
--- a/files/sudoers-mc
+++ b/files/sudoers-mc
@@ -1,2 +1,2 @@
 minecraft ALL=(ALL) NOPASSWD:/usr/bin/pkill
-minecraft ALL=(ALL) NOPASSWD:/usr/sbin/knockd
+minecraft ALL=(ALL) NOPASSWD:/usr/local/sbin/knockd
diff --git a/scripts/start-autopause b/scripts/start-autopause
index 66fbbe6..59d5c76 100755
--- a/scripts/start-autopause
+++ b/scripts/start-autopause
@@ -84,4 +84,9 @@ elif [[ -z "$MAX_TICK_TIME" ]] ; then
   export MAX_TICK_TIME
 fi
 
+# seq_cooldown cannot be larger than AUTOPAUSE_TIMEOUT_KN, otherwise the server may
+# become paused while knockd is still ignoring packets, preventing players from joining.
+let COOLDOWN=$AUTOPAUSE_TIMEOUT_KN/2
+sed -i "s/\(seq_cooldown *= *\).*/\1$COOLDOWN/" /tmp/knockd-config.cfg
+
 /auto/autopause-daemon.sh &