4 files changed, 52 insertions, 0 deletions
diff --git a/conn/controlfns.go b/conn/controlfns.go
index fe32871..4f7d90f 100644
--- a/conn/controlfns.go
+++ b/conn/controlfns.go
@@ -10,6 +10,13 @@ import (
 	"syscall"
 )
 
+// UDP socket read/write buffer size (7MB). The value of 7MB is chosen as it is
+// the max supported by a default configuration of macOS. Some platforms will
+// silently clamp the value to other maximums, such as linux clamping to
+// net.core.{r,w}mem_max (see _linux.go for additional implementation that works
+// around this limitation)
+const socketBufferSize = 7 << 20
+
 // controlFn is the callback function signature from net.ListenConfig.Control.
 // It is used to apply platform specific configuration to the socket prior to
 // bind.
diff --git a/conn/controlfns_linux.go b/conn/controlfns_linux.go
index 9e26d95..aff6245 100644
--- a/conn/controlfns_linux.go
+++ b/conn/controlfns_linux.go
@@ -15,6 +15,21 @@ import (
 func init() {
 	controlFns = append(controlFns,
 
+		// Attempt to set the socket buffer size beyond net.core.{r,w}mem_max by
+		// using SO_*BUFFORCE. This requires CAP_NET_ADMIN, and is allowed here to
+		// fail silently - the result of failure is lower performance on very fast
+		// links or high latency links.
+		func(network, address string, c syscall.RawConn) error {
+			return c.Control(func(fd uintptr) {
+				// Set up to *mem_max
+				_ = unix.SetsockoptInt(int(fd), unix.SOL_SOCKET, unix.SO_RCVBUF, socketBufferSize)
+				_ = unix.SetsockoptInt(int(fd), unix.SOL_SOCKET, unix.SO_SNDBUF, socketBufferSize)
+				// Set beyond *mem_max if CAP_NET_ADMIN
+				_ = unix.SetsockoptInt(int(fd), unix.SOL_SOCKET, unix.SO_RCVBUFFORCE, socketBufferSize)
+				_ = unix.SetsockoptInt(int(fd), unix.SOL_SOCKET, unix.SO_SNDBUFFORCE, socketBufferSize)
+			})
+		},
+
 		// Enable receiving of the packet information (IP_PKTINFO for IPv4,
 		// IPV6_PKTINFO for IPv6) that is used to implement sticky socket support.
 		func(network, address string, c syscall.RawConn) error {
diff --git a/conn/controlfns_unix.go b/conn/controlfns_unix.go
index 9738c73..c4536d4 100644
--- a/conn/controlfns_unix.go
+++ b/conn/controlfns_unix.go
@@ -16,6 +16,13 @@ import (
 func init() {
 	controlFns = append(controlFns,
 		func(network, address string, c syscall.RawConn) error {
+			return c.Control(func(fd uintptr) {
+				_ = unix.SetsockoptInt(int(fd), unix.SOL_SOCKET, unix.SO_RCVBUF, socketBufferSize)
+				_ = unix.SetsockoptInt(int(fd), unix.SOL_SOCKET, unix.SO_SNDBUF, socketBufferSize)
+			})
+		},
+
+		func(network, address string, c syscall.RawConn) error {
 			var err error
 			if network == "udp6" {
 				c.Control(func(fd uintptr) {
diff --git a/conn/controlfns_windows.go b/conn/controlfns_windows.go
new file mode 100644
index 0000000..c3bdf7d
--- /dev/null
+++ b/conn/controlfns_windows.go
@@ -0,0 +1,23 @@
+/* SPDX-License-Identifier: MIT
+ *
+ * Copyright (C) 2017-2023 WireGuard LLC. All Rights Reserved.
+ */
+
+package conn
+
+import (
+	"syscall"
+
+	"golang.org/x/sys/windows"
+)
+
+func init() {
+	controlFns = append(controlFns,
+		func(network, address string, c syscall.RawConn) error {
+			return c.Control(func(fd uintptr) {
+				_ = windows.SetsockoptInt(windows.Handle(fd), windows.SOL_SOCKET, windows.SO_RCVBUF, socketBufferSize)
+				_ = windows.SetsockoptInt(windows.Handle(fd), windows.SOL_SOCKET, windows.SO_SNDBUF, socketBufferSize)
+			})
+		},
+	)
+}