Add support for std::net::{Ipv4Addr, Ipv6Addr, IpAddr} <-> INET

[ivan]

Would you take a PR that does this? (I am working on one.)

[sfackler]

Postgres stores a netmask in addition to the IP address, which is why these implementations don't exist already.

[ivan]

Indeed, that is a bit of a troublesome mismatch. What I'm doing is: always writing 32 bits / 128 bits in ToSql, and doing something like

        if bits != 32 {
            let err: Box<error::Error + Sync + Send> = "INET must have all 32 bits for Ipv4Addr".into();
            return Err(Error::Conversion(err));
        }

in FromSql.

Do you think that is workable? This should at least support the use case where one does not store any netmasks other than the default /32 or /128.

[sfackler]

I would prefer that the implementations in this library be "lossless" in general.

[ivan]

I take your point. I guess I might want to make a new crate with types that wrap Ipv4Addr and Ipv6Addr to add a netmask.

[ivan]

I just figured out that there is a way to insert Ipv4Addr/Ipv6Addr using strings:

let ipv4_s = format!("{}", Ipv4Addr::new(127, 0, 0, 1));
let ipv6_s = format!("{}", Ipv6Addr::new(1, 2, 3, 4, 5, 6, 7, 8));
conn.execute("INSERT INTO sessions (last_seen_ipv4, last_seen_ipv6)
              VALUES (cast($1::text as inet), cast($2::text as inet))", &[&ipv4_s, &ipv6_s]).unwrap();

[zr40]

@ivan note that you can use $1::text::inet. Both cast syntaxes have the same meaning, you don't need to use both together.

[ivan]

Thanks! That does look a lot better.

[newpavlov]

@sfackler
How about just using a simple aliased tuple type MaskIpAddr = (IpAddr, u8); for lossless operations with inet and cidr?