Partial OpenBSD support.

Package.swift

@@ -59,6 +59,7 @@ let package = Package(
             dependencies: [
                 "NIOConcurrencyHelpers",
                 "_NIOBase64",
+                "CNIOOpenBSD",
                 "CNIODarwin",
                 "CNIOLinux",
                 "CNIOWindows",
@@ -91,6 +92,7 @@ let package = Package(
         .target(
             name: "NIOPosix",
             dependencies: [
+                "CNIOOpenBSD",
                 "CNIOLinux",
                 "CNIODarwin",
                 "CNIOWindows",
@@ -147,6 +149,10 @@ let package = Package(
             name: "CNIOSHA1",
             dependencies: []
         ),
+        .target(
+            name: "CNIOOpenBSD",
+            dependencies: []
+        ),
         .target(
             name: "CNIOLinux",
             dependencies: [],
@@ -482,6 +488,7 @@ let package = Package(
                 "NIOTestUtils",
                 "NIOConcurrencyHelpers",
                 "NIOEmbedded",
+                "CNIOOpenBSD",
                 "CNIOLinux",
                 "CNIODarwin",
                 "NIOTLS",

README.md

@@ -103,6 +103,8 @@ SwiftNIO aims to support all of the platforms where Swift is supported. Currentl
 * Ubuntu 18.04+
 * macOS 10.9+, iOS 7+; (macOS 10.14+, iOS 12+, tvOS 12+ or watchOS 6+ with [swift-nio-transport-services][repo-nio-transport-services])
 
+SwiftNIO has experimental support on OpenBSD for all SwiftNIO libraries _except_ for NIOFileSystem, which is not yet supported. You can use all other SwiftNIO libraries on OpenBSD by adding them as dependencies in `Package.swift`.
+
 ### Compatibility
 
 SwiftNIO follows [SemVer 2.0.0](https://semver.org/#semantic-versioning-200) with a separate document declaring [SwiftNIO's Public API](docs/public-api.md).

Sources/CNIOOpenBSD/include/CNIOOpenBSD.h

@@ -0,0 +1,101 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the SwiftNIO open source project
+//
+// Copyright (c) 2017-2025 Apple Inc. and the SwiftNIO project authors
+// Licensed under Apache License v2.0
+//
+// See LICENSE.txt for license information
+// See CONTRIBUTORS.txt for the list of SwiftNIO project authors
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+//===----------------------------------------------------------------------===//
+#ifndef C_NIO_OPENBSD_H
+#define C_NIO_OPENBSD_H
+
+#if defined(__OpenBSD__)
+#include <sys/types.h>
+#include <sys/event.h>
+#include <pthread_np.h>
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <sys/stat.h>
+#include <sys/time.h>
+#include <sys/un.h>
+#include <sys/utsname.h>
+#include <dirent.h>
+#include <fts.h>
+#include <ifaddrs.h>
+#include <net/if.h>
+#include <netinet/in.h>
+#include <netinet/ip.h>
+#include <pthread.h>
+#include <stdbool.h>
+
+
+// Some explanation is required here.
+//
+// Due to SR-6772, we cannot get Swift code to directly see any of the mmsg structures or
+// functions. However, we *can* get C code built by SwiftPM to see them. For this reason we
+// elect to provide a selection of shims to enable Swift code to use recv_mmsg and send_mmsg.
+// Mostly this is fine, but to minimise the overhead we want the Swift code to be able to
+// create the msgvec directly without requiring further memory fussiness in our C shim.
+// That requires us to also construct a C structure that has the same layout as struct mmsghdr.
+//
+// Conveniently glibc has pretty strict ABI stability rules, and this structure is part of the
+// glibc ABI, so we can just reproduce the structure definition here and feel confident that it
+// will be sufficient.
+//
+// If SR-6772 ever gets resolved we can remove this shim.
+//
+// https://bugs.swift.org/browse/SR-6772
+
+typedef struct {
+    struct msghdr msg_hdr;
+    unsigned int msg_len;
+} CNIOOpenBSD_mmsghdr;
+
+typedef struct {
+    struct in6_addr ipi6_addr;
+    unsigned int ipi6_ifindex;
+} CNIOOpenBSD_in6_pktinfo;
+
+int CNIOOpenBSD_sendmmsg(int sockfd, CNIOOpenBSD_mmsghdr *msgvec, unsigned int vlen, int flags);
+int CNIOOpenBSD_recvmmsg(int sockfd, CNIOOpenBSD_mmsghdr *msgvec, unsigned int vlen, int flags, struct timespec *timeout);
+
+int CNIOOpenBSD_pthread_set_name_np(pthread_t thread, const char *name);
+int CNIOOpenBSD_pthread_get_name_np(pthread_t thread, char *name, size_t len);
+
+// Non-standard socket stuff.
+int CNIOOpenBSD_accept4(int sockfd, struct sockaddr *addr, socklen_t *addrlen, int flags);
+
+// cmsghdr handling
+struct cmsghdr *CNIOOpenBSD_CMSG_FIRSTHDR(const struct msghdr *);
+struct cmsghdr *CNIOOpenBSD_CMSG_NXTHDR(struct msghdr *, struct cmsghdr *);
+const void *CNIOOpenBSD_CMSG_DATA(const struct cmsghdr *);
+void *CNIOOpenBSD_CMSG_DATA_MUTABLE(struct cmsghdr *);
+size_t CNIOOpenBSD_CMSG_LEN(size_t);
+size_t CNIOOpenBSD_CMSG_SPACE(size_t);
+
+// awkward time_T pain
+extern const int CNIOOpenBSD_SO_TIMESTAMP;
+extern const int CNIOOpenBSD_SO_RCVTIMEO;
+
+int CNIOOpenBSD_system_info(struct utsname *uname_data);
+
+extern const unsigned long CNIOOpenBSD_IOCTL_VM_SOCKETS_GET_LOCAL_CID;
+
+const char* CNIOOpenBSD_dirent_dname(struct dirent *ent);
+
+extern const unsigned long CNIOOpenBSD_UTIME_OMIT;
+extern const unsigned long CNIOOpenBSD_UTIME_NOW;
+
+extern const long CNIOOpenBSD_UDP_MAX_SEGMENTS;
+
+// A workaround for incorrect nullability annotations in the Android SDK.
+// Probably unnecessary on BSD, but copying for consistency for now.
+FTS *CNIOOpenBSD_fts_open(char * const *path_argv, int options, int (*compar)(const FTSENT **, const FTSENT **));
+
+#endif
+#endif

Sources/CNIOOpenBSD/shim.c

@@ -0,0 +1,131 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the SwiftNIO open source project
+//
+// Copyright (c) 2017-2025 Apple Inc. and the SwiftNIO project authors
+// Licensed under Apache License v2.0
+//
+// See LICENSE.txt for license information
+// See CONTRIBUTORS.txt for the list of SwiftNIO project authors
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+//===----------------------------------------------------------------------===//
+
+// Xcode's Archive builds with Xcode's Package support struggle with empty .c files
+// (https://bugs.swift.org/browse/SR-12939).
+void CNIOOpenBSD_i_do_nothing_just_working_around_a_darwin_toolchain_bug(void) {}
+
+#if defined(__OpenBSD__)
+
+#include <CNIOOpenBSD.h>
+#include <pthread.h>
+#include <assert.h>
+#include <unistd.h>
+
+int CNIOOpenBSD_pthread_set_name_np(pthread_t thread, const char *name) {
+    pthread_set_name_np(thread, name);
+    return 0;
+}
+
+int CNIOOpenBSD_pthread_get_name_np(pthread_t thread, char *name, size_t len) {
+    pthread_get_name_np(thread, name, len);
+    return 0;
+}
+
+int CNIOOpenBSD_sendmmsg(int sockfd, CNIOOpenBSD_mmsghdr *msgvec, unsigned int vlen, int flags) {
+    // This is technically undefined behaviour, but it's basically fine because these types are the same size, and we
+    // don't think the compiler is inclined to blow anything up here.
+    // This comment is from CNIOLinux, but I haven't reverified this applies for OpenBSD.
+    return sendmmsg(sockfd, (struct mmsghdr *)msgvec, vlen, flags);
+}
+
+int CNIOOpenBSD_recvmmsg(int sockfd, CNIOOpenBSD_mmsghdr *msgvec, unsigned int vlen, int flags, struct timespec *timeout) {
+    // This is technically undefined behaviour, but it's basically fine because these types are the same size, and we
+    // don't think the compiler is inclined to blow anything up here.
+    // This comment is from CNIOLinux, but I haven't reverified this applies for OpenBSD.
+    return recvmmsg(sockfd, (struct mmsghdr *)msgvec, vlen, flags, timeout);
+}
+
+int CNIOOpenBSD_accept4(int sockfd, struct sockaddr *addr, socklen_t *addrlen, int flags) {
+    return accept4(sockfd, addr, addrlen, flags);
+}
+
+struct cmsghdr *CNIOOpenBSD_CMSG_FIRSTHDR(const struct msghdr *mhdr) {
+    assert(mhdr != NULL);
+    return CMSG_FIRSTHDR(mhdr);
+}
+
+struct cmsghdr *CNIOOpenBSD_CMSG_NXTHDR(struct msghdr *mhdr, struct cmsghdr *cmsg) {
+    assert(mhdr != NULL);
+    assert(cmsg != NULL);
+    return CMSG_NXTHDR(mhdr, cmsg);
+}
+
+const void *CNIOOpenBSD_CMSG_DATA(const struct cmsghdr *cmsg) {
+    assert(cmsg != NULL);
+    return CMSG_DATA(cmsg);
+}
+
+void *CNIOOpenBSD_CMSG_DATA_MUTABLE(struct cmsghdr *cmsg) {
+    assert(cmsg != NULL);
+    return CMSG_DATA(cmsg);
+}
+
+size_t CNIOOpenBSD_CMSG_LEN(size_t payloadSizeBytes) {
+    return CMSG_LEN(payloadSizeBytes);
+}
+
+size_t CNIOOpenBSD_CMSG_SPACE(size_t payloadSizeBytes) {
+    return CMSG_SPACE(payloadSizeBytes);
+}
+
+const int CNIOOpenBSD_SO_TIMESTAMP = SO_TIMESTAMP;
+const int CNIOOpenBSD_SO_RCVTIMEO = SO_RCVTIMEO;
+
+bool supports_udp_sockopt(int opt, int value) {
+    int fd = socket(AF_INET, SOCK_DGRAM, 0);
+    if (fd == -1) {
+        return false;
+    }
+    int rc = setsockopt(fd, IPPROTO_UDP, opt, &value, sizeof(value));
+    close(fd);
+    return rc == 0;
+}
+
+bool CNIOOpenBSD_supports_udp_segment() {
+    #ifndef UDP_SEGMENT
+    return false;
+    #else
+    return supports_udp_sockopt(UDP_SEGMENT, 512);
+    #endif
+}
+
+bool CNIOOpenBSD_supports_udp_gro() {
+    #ifndef UDP_GRO
+    return false;
+    #else
+    return supports_udp_sockopt(UDP_GRO, 1);
+    #endif
+}
+
+int CNIOOpenBSD_system_info(struct utsname* uname_data) {
+    return uname(uname_data);
+}
+
+const char* CNIOOpenBSD_dirent_dname(struct dirent* ent) {
+    return ent->d_name;
+}
+
+const unsigned long CNIOOpenBSD_UTIME_OMIT = UTIME_OMIT;
+const unsigned long CNIOOpenBSD_UTIME_NOW = UTIME_NOW;
+
+#ifdef UDP_MAX_SEGMENTS
+const long CNIOOpenBSD_UDP_MAX_SEGMENTS = UDP_MAX_SEGMENTS;
+#endif
+const long CNIOOpenBSD_UDP_MAX_SEGMENTS = -1;
+
+FTS *CNIOOpenBSD_fts_open(char * const *path_argv, int options, int (*compar)(const FTSENT **, const FTSENT **)) {
+    return fts_open(path_argv, options, compar);
+}
+#endif

Sources/CNIOSHA1/c_nio_sha1.c

@@ -54,7 +54,7 @@
 #endif
 #ifdef __ANDROID__
 #include <sys/endian.h>
-#elif defined(__linux__) || defined(__APPLE__) || defined(__wasm32__)
+#elif defined(__linux__) || defined(__APPLE__) || defined(__wasm32__) || defined(__OpenBSD__)
 #include <sys/types.h>
 #elif defined(_WIN32) || defined(_WIN64)
 	#ifndef LITTLE_ENDIAN

Sources/NIOConcurrencyHelpers/NIOAtomic.swift

@@ -213,6 +213,7 @@ public final class NIOAtomic<T: NIOAtomicPrimitive> {
 
     /// Create an atomic object with `value`
     @inlinable
+    @available(OpenBSD, unavailable, message: "malloc_size is unavailable.")
     public static func makeAtomic(value: T) -> NIOAtomic {
         let manager = Manager(bufferClass: self, minimumCapacity: 1) { _, _ in }
         manager.withUnsafeMutablePointerToElements {

Sources/NIOConcurrencyHelpers/NIOLock.swift

@@ -35,6 +35,9 @@ import wasi_pthread
 #if os(Windows)
 @usableFromInline
 typealias LockPrimitive = SRWLOCK
+#elseif os(OpenBSD)
+@usableFromInline
+typealias LockPrimitive = pthread_mutex_t?
 #else
 @usableFromInline
 typealias LockPrimitive = pthread_mutex_t
@@ -50,6 +53,11 @@ extension LockOperations {
 
         #if os(Windows)
         InitializeSRWLock(mutex)
+        #elseif os(OpenBSD)
+        var attr = pthread_mutexattr_t(bitPattern: 0)
+        pthread_mutexattr_init(&attr)
+        let err = pthread_mutex_init(mutex, &attr)
+        precondition(err == 0, "\(#function) failed in pthread_mutex with error \(err)")
         #elseif (compiler(<6.1) && !os(WASI)) || (compiler(>=6.1) && _runtime(_multithreaded))
         var attr = pthread_mutexattr_t()
         pthread_mutexattr_init(&attr)

Sources/NIOConcurrencyHelpers/atomics.swift

@@ -463,6 +463,7 @@ extension UInt: AtomicPrimitive {
     deprecated,
     message: "AtomicBox is deprecated without replacement because the original implementation doesn't work."
 )
+@available(OpenBSD, unavailable, message: "malloc_size is unavailable.")
 public final class AtomicBox<T: AnyObject> {
     private let storage: NIOAtomic<UInt>
 
@@ -608,4 +609,5 @@ public final class AtomicBox<T: AnyObject> {
 }
 
 @available(*, deprecated)
+@available(OpenBSD, unavailable, message: "malloc_size is unavailable.")
 extension AtomicBox: @unchecked Sendable where T: Sendable {}

Sources/NIOConcurrencyHelpers/lock.swift

@@ -43,6 +43,9 @@ public final class Lock {
     #if os(Windows)
     fileprivate let mutex: UnsafeMutablePointer<SRWLOCK> =
         UnsafeMutablePointer.allocate(capacity: 1)
+    #elseif os(OpenBSD)
+    fileprivate let mutex: UnsafeMutablePointer<pthread_mutex_t?> =
+        UnsafeMutablePointer.allocate(capacity: 1)
     #else
     fileprivate let mutex: UnsafeMutablePointer<pthread_mutex_t> =
         UnsafeMutablePointer.allocate(capacity: 1)
@@ -52,6 +55,10 @@ public final class Lock {
     public init() {
         #if os(Windows)
         InitializeSRWLock(self.mutex)
+        #elseif os(OpenBSD)
+        var attr = pthread_mutexattr_t(bitPattern: 0)
+        let err = pthread_mutex_init(self.mutex, &attr)
+        precondition(err == 0, "\(#function) failed in pthread_mutex with error \(err)")
         #elseif (compiler(<6.1) && !os(WASI)) || (compiler(>=6.1) && _runtime(_multithreaded))
         var attr = pthread_mutexattr_t()
         pthread_mutexattr_init(&attr)
@@ -134,6 +141,9 @@ public final class ConditionLock<T: Equatable> {
     #if os(Windows)
     private let cond: UnsafeMutablePointer<CONDITION_VARIABLE> =
         UnsafeMutablePointer.allocate(capacity: 1)
+    #elseif os(OpenBSD)
+    private let cond: UnsafeMutablePointer<pthread_cond_t?> =
+        UnsafeMutablePointer.allocate(capacity: 1)
     #elseif (compiler(<6.1) && !os(WASI)) || (compiler(>=6.1) && _runtime(_multithreaded))
     private let cond: UnsafeMutablePointer<pthread_cond_t> =
         UnsafeMutablePointer.allocate(capacity: 1)

Sources/NIOCore/BSDSocketAPI.swift

@@ -83,6 +83,14 @@ private let sysInet_ntop:
         inet_ntop
 private let sysInet_pton: @convention(c) (CInt, UnsafePointer<CChar>?, UnsafeMutableRawPointer?) -> CInt = inet_pton
 #endif
+#elseif os(OpenBSD)
+@preconcurrency import Glibc
+import CNIOOpenBSD
+
+private let sysInet_ntop:
+    @convention(c) (CInt, UnsafeRawPointer?, UnsafeMutablePointer<CChar>?, socklen_t) -> UnsafePointer<CChar>? =
+        inet_ntop
+private let sysInet_pton: @convention(c) (CInt, UnsafePointer<CChar>?, UnsafeMutableRawPointer?) -> CInt = inet_pton
 #elseif canImport(Darwin)
 import Darwin