x/sys/unix: Sockaddr for AF_IUCV missing

[bluecmd]

What version of Go are you using (go version)?

$ go version
go version go1.15 linux/s390x

Does this issue reproduce with the latest release?

Yes

What operating system and processor architecture are you using (go env)?

N/A

What did you do?

I try to use AF_IUCV with unix.Connect.
However there is no equivalent to sockaddr_iucv, and the interfaces are private so I cannot create one myself.

What did you expect to see?

A SockaddrIUCV structure that allows me to use AF_IUCV.

What did you see instead?

An impossible scenario where I need to use unix.Syscall directly instead.

[bluecmd]

I am thinking maybe something like the following. The C.struct_sockaddr_iucv is 100% untested cargo-cult, no idea if that works, and not clear what I need to do to test it.

diff --git a/unix/linux/types.go b/unix/linux/types.go
index 31a20c7..419ed24 100644
--- a/unix/linux/types.go
+++ b/unix/linux/types.go
@@ -540,6 +540,8 @@ type RawSockaddrL2TPIP C.struct_sockaddr_l2tpip
 
 type RawSockaddrL2TPIP6 C.struct_sockaddr_l2tpip6
 
+type RawSockaddrIUCV C.struct_sockaddr_iucv
+
 type RawSockaddr C.struct_sockaddr
 
 type RawSockaddrAny C.struct_sockaddr_any
@@ -594,6 +596,7 @@ const (
        SizeofSockaddrTIPC      = C.sizeof_struct_sockaddr_tipc
        SizeofSockaddrL2TPIP    = C.sizeof_struct_sockaddr_l2tpip
        SizeofSockaddrL2TPIP6   = C.sizeof_struct_sockaddr_l2tpip6
+       SizeofSockaddrIUCV      = C.sizeof_struct_sockaddr_iucv
        SizeofLinger            = C.sizeof_struct_linger
        SizeofIovec             = C.sizeof_struct_iovec
        SizeofIPMreq            = C.sizeof_struct_ip_mreq
diff --git a/unix/syscall_linux.go b/unix/syscall_linux.go
index 027bcaf..f66c515 100644
--- a/unix/syscall_linux.go
+++ b/unix/syscall_linux.go
@@ -885,6 +885,25 @@ func (sa *SockaddrL2TPIP6) sockaddr() (unsafe.Pointer, _Socklen, error) {
        return unsafe.Pointer(&sa.raw), SizeofSockaddrL2TPIP6, nil
 }
 
+// SockaddrIUCV implements the Sockaddr interface for AF_IUCV sockets.
+type SockaddrIUCV struct {
+       UserID string
+       Name   string
+       raw    RawSockaddrIUCV
+}
+
+func (sa *SockaddrIUCV) sockaddr() (unsafe.Pointer, _Socklen, error) {
+       sa.raw.Family = AF_IUCV
+       for i := 0; i < 8; i++ {
+               sa.raw.Nodeid[i] = ' '
+               sa.raw.User_id[i] = ' '
+               sa.raw.Name[i] = ' '
+       }
+       copy(sa.raw.User_id[:], []byte(sa.UserID))
+       copy(sa.raw.Name[:], []byte(sa.Name))
+       return unsafe.Pointer(&sa.raw), SizeofSockaddrIUCV, nil
+}
+
 func anyToSockaddr(fd int, rsa *RawSockaddrAny) (Sockaddr, error) {
        switch rsa.Addr.Family {
        case AF_NETLINK:
diff --git a/unix/ztypes_linux.go b/unix/ztypes_linux.go
index 83364d7..801f042 100644
--- a/unix/ztypes_linux.go
+++ b/unix/ztypes_linux.go
@@ -310,6 +310,15 @@ type RawSockaddrL2TPIP6 struct {
        Conn_id  uint32
 }
 
+type RawSockaddrIUCV struct {
+       Family   uint16
+       Port     uint16
+       Addr     uint32
+       Nodeid   [8]byte
+       User_id  [8]byte
+       Name     [8]byte
+}
+
 type _Socklen uint32
 
 type Linger struct {
@@ -422,6 +431,7 @@ const (
        SizeofSockaddrTIPC      = 0x10
        SizeofSockaddrL2TPIP    = 0x10
        SizeofSockaddrL2TPIP6   = 0x20
+       SizeofSockaddrIUCV      = 0x20
        SizeofLinger            = 0x8
        SizeofIPMreq            = 0x8
        SizeofIPMreqn           = 0xc

This makes it possible to dial IUCV like this:

package main

import (
  "log"

  "golang.org/x/sys/unix"
)

func main() {
  sock, _ := unix.Socket(unix.AF_IUCV, unix.SOCK_SEQPACKET, 0)
  sa := &unix.SockaddrIUCV{UserID: "TCPIP", Name: "IUCVTEST"}
  if err := unix.Connect(sock, sa); err != nil {
    log.Fatalf("IUCV connect failed: %v", err)
  }
}

[gopherbot]

Change https://golang.org/cl/248777 mentions this issue: unix: add AF_IUCV and SockaddrIUCV

[bluecmd]

🎉