Hi all, I'm working on adding a new Linux socket type (L2TPIP) to the unix package, and I noticed some code in there that appears on the face of it to be assuming the endianess of the host. The #networking channel on the Gophers slack suggested I raise the question here.
The code I am struggling with is in this file: https://github.com/golang/sys/blob/master/unix/syscall_linux.go So far as I can make out, this code implements a variety of system calls for Linux generally, irrespective of GOARCH. In this file, there is a function anyToSockaddr which serves to convert struct sockaddr from system calls such as getsockname(2) and accept4(2) into Go representations of the various sockaddr types, for example unix.SockaddrUnix and unix.SockaddrInet4. The function anyToSockaddr switches on the address family in the struct sockaddr, and then converts based on that. I noticed for the AF_INET case in the switch statement of anyToSockaddr that the struct sockaddr_in sin_port field is being unconditionally byte-swapped during conversion: pp := (*RawSockaddrInet4)(unsafe.Pointer(rsa)) sa := new(SockaddrInet4) p := (*[2]byte)(unsafe.Pointer(&pp.Port)) sa.Port = int(p[0])<<8 + int(p[1]) for i := 0; i < len(sa.Addr); i++ { sa.Addr[i] = pp.Addr[i] } return sa, nil (where 'rsa' is a pointer to a RawSockaddrAny). Now, ip(7) states of the struct sockaddr_in structure: "Note that the address and the port are always stored in network byte order. In particular, this means that you need to call htons(3) on the number that is assigned to a port." So the byte swapping that anyToSockaddr is doing makes sense, but only if the host is a little-endian machine. It seems as though this code would do the wrong thing on a big-endian machine. Can anyone suggest what I'm missing here? Is this code really assuming that the host is a little-endian machine? Thanks! Tom -- You received this message because you are subscribed to the Google Groups "golang-nuts" group. To unsubscribe from this group and stop receiving emails from it, send an email to golang-nuts+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/golang-nuts/b13ec1b5-7779-4abe-9c4f-cd4a06ce45aa%40googlegroups.com.
