feat: set IP_DONTFRAG on macOS

spikecurtis · spikecurtis · commit ef3f81d39f70 · 2025-06-09T11:12:18.000+04:00
diff --git a/wgengine/magicsock/magicsock_darwin.go b/wgengine/magicsock/magicsock_darwin.go
@@ -15,13 +15,13 @@ func trySetPathMTUDiscover(pconn nettype.PacketConn, logf logger.Logf, network s
 			logf("magicsock: failed to set Path MTU Discover: get syscall conn: %v", err)
 		}
 		level := unix.IPPROTO_IP
-		option := unix.IP_MTU_DISCOVER
+		option := unix.IP_DONTFRAG
 		if network == "udp6" {
 			level = unix.IPPROTO_IPV6
-			option = unix.IPV6_MTU_DISCOVER
+			option = unix.IPV6_DONTFRAG
 		}
 		err = s.Control(func(fd uintptr) {
-			err := unix.SetsockoptInt(int(fd), level, option, unix.IP_PMTUDISC_DO)
+			err := unix.SetsockoptInt(int(fd), level, option, 1)
 			if err != nil {
 				logf("magicsock: failed to set Path MTU Discover: SetsockoptInt failed: %v", err)
 			}

Original file line number	Diff line number	Diff line change
`@@ -15,13 +15,13 @@ func trySetPathMTUDiscover(pconn nettype.PacketConn, logf logger.Logf, network s`
`15`	`15`	`logf("magicsock: failed to set Path MTU Discover: get syscall conn: %v", err)`
`16`	`16`	`}`
`17`	`17`	`level := unix.IPPROTO_IP`
`18`		`- option := unix.IP_MTU_DISCOVER`
	`18`	`+ option := unix.IP_DONTFRAG`
`19`	`19`	`if network == "udp6" {`
`20`	`20`	`level = unix.IPPROTO_IPV6`
`21`		`- option = unix.IPV6_MTU_DISCOVER`
	`21`	`+ option = unix.IPV6_DONTFRAG`
`22`	`22`	`}`
`23`	`23`	`err = s.Control(func(fd uintptr) {`
`24`		`- err := unix.SetsockoptInt(int(fd), level, option, unix.IP_PMTUDISC_DO)`
	`24`	`+ err := unix.SetsockoptInt(int(fd), level, option, 1)`
`25`	`25`	`if err != nil {`
`26`	`26`	`logf("magicsock: failed to set Path MTU Discover: SetsockoptInt failed: %v", err)`
`27`	`27`	`}`