net: WriteToIP generates "socket is already connected" error

[gopherbot]

by chris@chrisduffin.org:

The following code generates a "socket is already connected" error in OS X.
Error does not occur in Linux.

package main

import (
    "fmt"
    "net"
)

func main() {
    dest := "192.168.2.253"
    host := "192.168.2.56"
    sendpkt := []byte{'r', 'o', 'a', 'd'}
    remote, err := net.ResolveIPAddr("ip4", dest)
    local, err := net.ResolveIPAddr("ip4", host)
    if err != nil {
        fmt.Printf("Could not parse IP address", 1)
    }
    ipconn, err := net.DialIP("ip4:icmp", local, remote)
    if err != nil {
        fmt.Printf("Could not create connection to %s", remote)
    }

    n, err := ipconn.WriteToIP(sendpkt, remote)
    if err != nil {
        fmt.Printf(`net.WriteToIP(..., %v) = %v, %v`, remote, n, err)
    }

}


Prints:

sudo ./ping                                                                             
                                                                                        
                                                                                 ⏎
net.WriteToIP(..., 192.168.2.253) = 0, write ip4 192.168.2.253: socket is already
connected%

[ianlancetaylor]

Comment 1:

Labels changed: added repo-main, release-go1.4.

[mikioh]

Comment 2:

Please don't use WriteTo/WriteToIP methods to connected-mode raw sockets. Almost all the
platforms prohibit this behavior,
> Error does not occur in Linux.
except Linux.

Labels changed: removed release-go1.4.

[gopherbot]

Comment 4:

CL https://golang.org/cl/97810043 mentions this issue.

[mikioh]

Comment 5:

This issue was closed by revision 7e41abb.

Status changed to Fixed.