sockoptip4_posix_nonlinux.go

     1  // Copyright 2011 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 (unix && !linux) || windows
     6  
     7  package net
     8  
     9  import (
    10  	"internal/bytealg"
    11  	"runtime"
    12  	"syscall"
    13  )
    14  
    15  func joinIPv4Group(fd *netFD, ifi *Interface, ip IP) error {
    16  	mreq := &syscall.IPMreq{Multiaddr: [4]byte{ip[0], ip[1], ip[2], ip[3]}}
    17  	if err := setIPv4MreqToInterface(mreq, ifi); err != nil {
    18  		return err
    19  	}
    20  	err := fd.pfd.SetsockoptIPMreq(syscall.IPPROTO_IP, syscall.IP_ADD_MEMBERSHIP, mreq)
    21  	runtime.KeepAlive(fd)
    22  	return wrapSyscallError("setsockopt", err)
    23  }
    24  
    25  func setIPv4MreqToInterface(mreq *syscall.IPMreq, ifi *Interface) error {
    26  	if ifi == nil {
    27  		return nil
    28  	}
    29  	ifat, err := ifi.Addrs()
    30  	if err != nil {
    31  		return err
    32  	}
    33  	for _, ifa := range ifat {
    34  		switch v := ifa.(type) {
    35  		case *IPAddr:
    36  			if a := v.IP.To4(); a != nil {
    37  				copy(mreq.Interface[:], a)
    38  				goto done
    39  			}
    40  		case *IPNet:
    41  			if a := v.IP.To4(); a != nil {
    42  				copy(mreq.Interface[:], a)
    43  				goto done
    44  			}
    45  		}
    46  	}
    47  done:
    48  	if bytealg.Equal(mreq.Interface[:], IPv4zero.To4()) {
    49  		return errNoSuchMulticastInterface
    50  	}
    51  	return nil
    52  }
    53
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