udp_darwin.go

     1  // Copyright 2023 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  //go:build darwin
     6  
     7  package quic
     8  
     9  import (
    10  	"encoding/binary"
    11  	"syscall"
    12  )
    13  
    14  // These socket options are available on darwin, but are not in the syscall
    15  // package. Since syscall package is frozen, just define them manually here.
    16  const (
    17  	ip_recvtos       = 0x1b
    18  	ipv6_recvpktinfo = 0x3d
    19  	ipv6_pktinfo     = 0x2e
    20  )
    21  
    22  // See udp.go.
    23  const (
    24  	udpECNSupport              = true
    25  	udpInvalidLocalAddrIsError = true
    26  )
    27  
    28  // Confusingly, on Darwin the contents of the IP_TOS option differ depending on whether
    29  // it is used as an inbound or outbound cmsg.
    30  
    31  func parseIPTOS(b []byte) (ecnBits, bool) {
    32  	// Single byte. The low two bits are the ECN field.
    33  	if len(b) != 1 {
    34  		return 0, false
    35  	}
    36  	return ecnBits(b[0] & ecnMask), true
    37  }
    38  
    39  func appendCmsgECNv4(b []byte, ecn ecnBits) []byte {
    40  	// 32-bit integer.
    41  	// https://github.com/apple/darwin-xnu/blob/2ff845c2e033bd0ff64b5b6aa6063a1f8f65aa32/bsd/netinet/in_tclass.c#L1062-L1073
    42  	b, data := appendCmsg(b, syscall.IPPROTO_IP, syscall.IP_TOS, 4)
    43  	binary.NativeEndian.PutUint32(data, uint32(ecn))
    44  	return b
    45  }
    46
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