Unexpected Error When Creating RAW Socket Without Sudo

jibarra · May 5, 2025, 9:37pm

Hey guys,

Why is this error.Unexpected rather than error.AccessDenied?

I’m attempting to create a raw socket using std.posix. When running my program without sudo I’m getting an unknown error. Running with sudo returns no error. Im a noob so if someone could enlighten me that would be cool .

Function call:

const socket: std.posix.socket_t =  try std.posix.socket(std.posix.AF.INET, std.posix.SOCK.RAW, std.posix.IPPROTO.ICMP)

Im running zig 0.14.0 on popOS.

cryptocode · May 5, 2025, 10:05pm

Hey, and welcome to the forum! The error you see is not a Zig issue per se. It’s due to raw sockets requiring special permissions on your OS.

You can use setcap to set this capability on the executable as explained here

dimdin · May 5, 2025, 10:43pm

Welcome to ziggit @jibarra

Zig handles all the error number cases listed in macos and linux manual page for man 2 socket, including EACCES defined as errno 13, meaning “Permission denied”.
But the linux man page also says:

Other errors may be generated by the underlying protocol modules.

The manual page man 7 packet lists some more error numbers that the zig source code of socket currently does not handle. For example EPERM is defined as errno 1, meaning “Operation not permitted”, with the following description in the manual page:

User has insufficient privileges to carry out this operation.

What is the error number displayed after the message unexpected errno: ?

kj4tmp · May 6, 2025, 2:58am

github.com/ziglang/zig

`E.PERM` should not be an unexpected error for `std.posix.socket`

opened 05:26AM - 07 Jul 24 UTC

kj4tmp

bug contributor friendly standard library

### Zig Version 0.14.0-dev.66+1fdf13a14 ### Steps to Reproduce and Observe…d Output this test outputs the following when not run with sudo: ``` error: 'main.test.socket permissions error' failed: unexpected errno: 1 ``` errno 1 corresponds to `E.PERM` (permission denied when creating socket) This errno is expected because creating a raw socket generally requires elevated privileges. ```zig test "socket permissions error" { const ETH_P_ETHERCAT: u16 = 0x88a4; const socket_result = std.posix.socket( std.posix.AF.PACKET, std.posix.SOCK.RAW, std.mem.nativeToBig(u32, ETH_P_ETHERCAT), ); try std.testing.expect(socket_result == std.posix.SocketError.PermissionDenied); } ``` this is because std.posix.socket does not expect `.PERM`: https://github.com/ziglang/zig/blob/master/lib/std/posix.zig#L3519 ```zig switch (errno(rc)) { .SUCCESS => { const fd: fd_t = @intCast(rc); errdefer close(fd); if (!have_sock_flags) { try setSockFlags(fd, socket_type); } return fd; }, // <------------------ .PERM is missing here! .ACCES => return error.PermissionDenied, .AFNOSUPPORT => return error.AddressFamilyNotSupported, .INVAL => return error.ProtocolFamilyNotAvailable, .MFILE => return error.ProcessFdQuotaExceeded, .NFILE => return error.SystemFdQuotaExceeded, .NOBUFS => return error.SystemResources, .NOMEM => return error.SystemResources, .PROTONOSUPPORT => return error.ProtocolNotSupported, .PROTOTYPE => return error.SocketTypeNotSupported, else => |err| return unexpectedErrno(err), } } ``` when `.PERM` is is actually expected. So the switch should probably have the following in it: ```zig .PERM => return error.PermissionDenied, ``` ### Expected Output we expect `std.posix.socket` to return `error.PermissionDenied` when the syscall returns `E.PERM`.

jibarra · May 6, 2025, 3:45pm

Thanks for sharing this!

jibarra · May 6, 2025, 3:47pm

You’re totally right I am getting errno 1. This exactly answered my question, Thanks!