Remove redundant unsafe in talpid-net

[MarkusPettersson98]

This PR aims to write talpid-net/src/unix.rs in a more idiomatic way by wrapping the call to ioctl in a struct with a vetted constructor (IfReq::new) and safe methods. I managed to consolidate some unsafe blocks as well, which reduced the number of unsafe blocks from 7 to 5.:)

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This change is 

[hulthe]

Reviewable status: 0 of 1 files reviewed, 1 unresolved discussion (waiting on @MarkusPettersson98)

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talpid-net/src/unix.rs line 59 at r1 (raw file):

        let interface_name = interface.as_bytes();
        if interface_name.len() > nix::libc::IF_NAMESIZE {
            return Err(invalid_input("Interface name too long"));

I think, based on this SO-thread i found, that you need to leave space for a null bytes at the end. So this is the correct comparison (note the >=):

// Check that the name (plus a null byte) fits into IF_NAMESIZE
if interface_name.len() >= nix::libc::IF_NAMESIZE {
    return Err(invalid_input("Interface name too long"));
}

[hulthe]

Reviewable status: 0 of 1 files reviewed, 2 unresolved discussions (waiting on @MarkusPettersson98)

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talpid-net/src/unix.rs line 64 at r1 (raw file):

        let mut ifr: ifreq = unsafe { mem::zeroed() };
        // SAFETY: `interface_name.len()` does not exceed IF_NAMESIZE and `interface_name` only
        // contains ASCII.

Write something about the null terminator here also maybe

[MarkusPettersson98]

Reviewable status: 0 of 1 files reviewed, 1 unresolved discussion (waiting on @hulthe)

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talpid-net/src/unix.rs line 59 at r1 (raw file):

Previously, hulthe (Joakim Hulthe) wrote…

I think, based on this SO-thread i found, that you need to leave space for a null bytes at the end. So this is the correct comparison (note the >=):

// Check that the name (plus a null byte) fits into IF_NAMESIZE
if interface_name.len() >= nix::libc::IF_NAMESIZE {
    return Err(invalid_input("Interface name too long"));
}

Good catch! I interpreted the netdevice source code the same way: https://www.man7.org/linux/man-pages/man7/netdevice.7.html

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talpid-net/src/unix.rs line 64 at r1 (raw file):

Previously, hulthe (Joakim Hulthe) wrote…

Write something about the null terminator here also maybe

Done

[hulthe]

I feel like this could even be upstreamed to nix

@hulthe reviewed 1 of 1 files at r2, all commit messages.
Reviewable status: all files reviewed, 1 unresolved discussion (waiting on @MarkusPettersson98)

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talpid-net/src/unix.rs line 74 at r2 (raw file):

Domain::IPV4

I know you didn't change this, but does it really work for ipv6?

[MarkusPettersson98]

<3 I might look into it! It would be a very welcome addition:-)

Reviewable status: all files reviewed, 1 unresolved discussion (waiting on @hulthe)

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talpid-net/src/unix.rs line 74 at r2 (raw file):

Previously, hulthe (Joakim Hulthe) wrote…

Domain::IPV4

I know you didn't change this, but does it really work for ipv6?

That's a great question. I'll run some checks and try to dig into it.