Also provide musl libc builds of Velocity natives

Reference: PaperMC/Paper#11367

native/README.md

@@ -18,13 +18,11 @@ CommonCrypto library.
 - macOS aarch64 ("Apple Silicon")
 
 For Linux platforms, we provide two versions of the native library: one built against OpenSSL 1.1.x and one built against OpenSSL 3.x.x.
-All native libraries are built on various versions of Ubuntu:
+All native libraries are built on various versions of Ubuntu and Alpine:
 
 - Ubuntu 20.04 for OpenSSL 1.1.x support and for compression
 - Ubuntu 22.04 for OpenSSL 3.x.x support
-
-Currently, we do not provide native libraries for distributions based on musl libc, like Alpine Linux. You might be able to use `apk add libc6-compat` to fake it, but this is not officially supported.
-In the future we may provide a musl libc build.
+- Alpine 3.18 for OpenSSL 3.x.x support and compression (musl libc users only)
 
 ## Building
 

native/build-support/alpine.Dockerfile

@@ -0,0 +1,9 @@
+
+FROM amazoncorretto:17.0.12-alpine3.18
+
+# Install required dependencies
+RUN apk add --no-cache bash alpine-sdk cmake openssl-dev openssl
+
+# Create a non-root user
+RUN adduser -D user
+USER user

native/build-support/build-all-linux-natives.sh

@@ -6,7 +6,8 @@ set -e
 cd "$(dirname "$0")/.." || exit 1
 
 ARCHS=(x86_64 aarch64)
-BASE_DOCKERFILE_VARIANTS=(ubuntu-focal ubuntu-jammy)
+BASE_DOCKERFILE_VARIANTS=(ubuntu-focal ubuntu-jammy alpine)
+COMPRESSION_VARIANTS=(ubuntu-focal alpine)
 
 for variant in "${BASE_DOCKERFILE_VARIANTS[@]}"; do
   docker_platforms=""
@@ -25,8 +26,8 @@ for arch in "${ARCHS[@]}"; do
     docker run --rm -v "$(pwd)":/app --platform linux/${arch} velocity-native-build:$variant /bin/bash -c "cd /app && ./build-support/compile-linux-crypto.sh"
   done
 
-  # Use only the oldest variant for the compression library
-  variant=${BASE_DOCKERFILE_VARIANTS[0]}
+  for variant in "${COMPRESSION_VARIANTS[@]}"; do
     echo "Building native compression for $arch on $variant..."
     docker run --rm -v "$(pwd)":/app --platform linux/${arch} velocity-native-build:$variant /bin/bash -c "cd /app && ./build-support/compile-linux-compress.sh"
+  done
 done

native/build-support/compile-linux-compress.sh

@@ -16,8 +16,14 @@ cd libdeflate || exit
 rm -rf build && cmake -DCMAKE_POSITION_INDEPENDENT_CODE=ON -B build && cmake --build build --target libdeflate_static
 cd ..
 
+# Determine if we are on musl libc or glibc
+suffix=""
+if ldd --version 2>&1 | grep -q musl; then
+  suffix="-musl"
+fi
+
 CFLAGS="-O2 -I$JAVA_HOME/include/ -I$JAVA_HOME/include/linux/ -fPIC -shared -Wl,-z,noexecstack -Wall -Werror -fomit-frame-pointer"
 ARCH=$(uname -m)
 mkdir -p src/main/resources/linux_$ARCH
 $CC $CFLAGS -Ilibdeflate src/main/c/jni_util.c src/main/c/jni_zlib_deflate.c src/main/c/jni_zlib_inflate.c \
-    libdeflate/build/libdeflate.a -o src/main/resources/linux_$ARCH/velocity-compress.so
+    libdeflate/build/libdeflate.a -o src/main/resources/linux_$ARCH/velocity-compress$suffix.so

native/build-support/compile-linux-crypto.sh

@@ -20,9 +20,11 @@ if [ ! "$CC" ]; then
   export CC=gcc
 fi
 
-output_file="velocity-cipher.so"
-if [ -n "$OPENSSL_VERSION" ]; then
-  output_file="velocity-cipher-ossl${OPENSSL_VERSION}.so"
+# Determine if we are on musl libc or glibc
+suffix=""
+if ldd --version 2>&1 | grep -q musl; then
+  suffix="-musl"
+  filename=$(echo "$filename" | sed "s/\.so/$suffix.so/")
 fi
 
 CFLAGS="-O2 -I$JAVA_HOME/include/ -I$JAVA_HOME/include/linux/ -fPIC -shared -Wl,-z,noexecstack -Wall -Werror -fomit-frame-pointer"

native/src/main/java/com/velocitypowered/natives/util/NativeConstraints.java

@@ -19,6 +19,7 @@ package com.velocitypowered.natives.util;
 
 import io.netty.buffer.ByteBuf;
 import io.netty.buffer.Unpooled;
+import java.nio.charset.StandardCharsets;
 import java.util.function.BooleanSupplier;
 
 /**
@@ -29,6 +30,8 @@ public class NativeConstraints {
   private static final boolean IS_AMD64;
   private static final boolean IS_AARCH64;
   private static final boolean CAN_GET_MEMORYADDRESS;
+  private static final boolean IS_LINUX;
+  private static final boolean IS_MUSL_LIBC;
 
   static {
     ByteBuf test = Unpooled.directBuffer();
@@ -41,17 +44,44 @@ public class NativeConstraints {
     String osArch = System.getProperty("os.arch", "");
     IS_AMD64 = osArch.equals("amd64") || osArch.equals("x86_64");
     IS_AARCH64 = osArch.equals("aarch64") || osArch.equals("arm64");
+
+    IS_LINUX = System.getProperty("os.name", "").equalsIgnoreCase("Linux");
+
+    // Determine if we're using musl libc by invoking `ldd --version`.
+    if (IS_LINUX) {
+      boolean isMusl;
+      try {
+        Process process = new ProcessBuilder("ldd", "--version")
+            .redirectErrorStream(true)
+            .start();
+        process.waitFor();
+        try (var reader = process.getInputStream()) {
+          byte[] outputRaw = reader.readAllBytes();
+          String output = new String(outputRaw, StandardCharsets.UTF_8);
+          isMusl = output.contains("musl");
+        }
+      } catch (Exception e) {
+        isMusl = false;
+      }
+      IS_MUSL_LIBC = isMusl;
+    } else {
+      IS_MUSL_LIBC = false;
+    }
   }
 
   static final BooleanSupplier NATIVE_BASE = () -> NATIVES_ENABLED && CAN_GET_MEMORYADDRESS;
 
   static final BooleanSupplier LINUX_X86_64 = () -> NATIVE_BASE.getAsBoolean()
-      && System.getProperty("os.name", "").equalsIgnoreCase("Linux")
-      && IS_AMD64;
+      && IS_LINUX && IS_AMD64 && !IS_MUSL_LIBC;
+
+  static final BooleanSupplier LINUX_X86_64_MUSL = () -> NATIVE_BASE.getAsBoolean()
+      && IS_LINUX && IS_AMD64 && IS_MUSL_LIBC;
 
   static final BooleanSupplier LINUX_AARCH64 = () -> NATIVE_BASE.getAsBoolean()
-      && System.getProperty("os.name", "").equalsIgnoreCase("Linux")
-      && IS_AARCH64;
+      && IS_LINUX && IS_AARCH64 && !IS_MUSL_LIBC;
+
+  static final BooleanSupplier LINUX_AARCH64_MUSL = () -> NATIVE_BASE.getAsBoolean()
+      && IS_LINUX && IS_AARCH64 && IS_MUSL_LIBC;
 
   static final BooleanSupplier MACOS_AARCH64 = () -> NATIVE_BASE.getAsBoolean()
       && System.getProperty("os.name", "").equalsIgnoreCase("Mac OS X")

native/src/main/java/com/velocitypowered/natives/util/Natives.java

@@ -83,11 +83,21 @@ public class Natives {
           new NativeCodeLoader.Variant<>(NativeConstraints.LINUX_X86_64,
               copyAndLoadNative("/linux_x86_64/velocity-compress.so"),
               "libdeflate (Linux x86_64)",
-              LibdeflateVelocityCompressor.FACTORY), // compiled with Debian 10
+              LibdeflateVelocityCompressor.FACTORY), // compiled with Ubuntu 20.04
+          new NativeCodeLoader.Variant<>(NativeConstraints.LINUX_X86_64_MUSL,
+              copyAndLoadNative("/linux_x86_64/velocity-compress-musl.so"),
+              "libdeflate (Linux x86_64, musl)",
+              LibdeflateVelocityCompressor.FACTORY), // compiled with Alpine 3.18
+
           new NativeCodeLoader.Variant<>(NativeConstraints.LINUX_AARCH64,
               copyAndLoadNative("/linux_aarch64/velocity-compress.so"),
               "libdeflate (Linux aarch64)",
-              LibdeflateVelocityCompressor.FACTORY), // compiled with Fedora 36
+              LibdeflateVelocityCompressor.FACTORY), // compiled with Ubuntu 20.04
+          new NativeCodeLoader.Variant<>(NativeConstraints.LINUX_AARCH64_MUSL,
+              copyAndLoadNative("/linux_aarch64/velocity-compress-musl.so"),
+              "libdeflate (Linux aarch64, musl)",
+              LibdeflateVelocityCompressor.FACTORY), // compiled with Alpine 3.18
+
           new NativeCodeLoader.Variant<>(NativeConstraints.MACOS_AARCH64,
               copyAndLoadNative("/macos_arm64/velocity-compress.dylib"),
               "libdeflate (macOS ARM64 / Apple Silicon)",
@@ -108,6 +118,9 @@ public class Natives {
           new NativeCodeLoader.Variant<>(NativeConstraints.LINUX_X86_64,
               copyAndLoadNative("/linux_x86_64/velocity-cipher-ossl11x.so"), // Ubuntu 20.04
               "OpenSSL 1.1.x (Linux x86_64)", NativeVelocityCipher.FACTORY),
+          new NativeCodeLoader.Variant<>(NativeConstraints.LINUX_X86_64_MUSL,
+              copyAndLoadNative("/linux_x86_64/velocity-cipher-ossl30x-musl.so"), // Alpine 3.18
+              "OpenSSL 3.x.x (Linux x86_64, musl)", NativeVelocityCipher.FACTORY),
 
           new NativeCodeLoader.Variant<>(NativeConstraints.LINUX_AARCH64,
               copyAndLoadNative("/linux_aarch64/velocity-cipher.so"),
@@ -118,6 +131,9 @@ public class Natives {
           new NativeCodeLoader.Variant<>(NativeConstraints.LINUX_AARCH64,
               copyAndLoadNative("/linux_aarch64/velocity-cipher-ossl11x.so"),
               "OpenSSL 1.1.x (Linux aarch64)", NativeVelocityCipher.FACTORY), // Ubuntu 20.04
+          new NativeCodeLoader.Variant<>(NativeConstraints.LINUX_AARCH64_MUSL,
+              copyAndLoadNative("/linux_aarch64/velocity-cipher-ossl30x-musl.so"),
+              "OpenSSL 1.1.x (Linux aarch64, musl)", NativeVelocityCipher.FACTORY), // Alpine 3.18
 
           new NativeCodeLoader.Variant<>(NativeConstraints.MACOS_AARCH64,
               copyAndLoadNative("/macos_arm64/velocity-cipher.dylib"),