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feat: Add TTL connection param to multicast #1842

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Merged
Mallets merged 4 commits into from
Mar 21, 2025
Merged

feat: Add TTL connection param to multicast #1842

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113e3a2
feat: Add TTL connection param to multicast
Mar 18, 2025
4ae5ad6
Cargo fmt
Mallets Mar 20, 2025
8f2d13e
fix: apply suggestion from review comment
Mar 20, 2025
fa3aa05
Cargo fmt
Mallets Mar 21, 2025
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1 change: 1 addition & 0 deletions io/zenoh-links/zenoh-link-udp/src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -107,6 +107,7 @@ impl LocatorInspector for UdpLocatorInspector {
pub mod config {
pub const UDP_MULTICAST_IFACE: &str = "iface";
pub const UDP_MULTICAST_JOIN: &str = "join";
pub const UDP_MULTICAST_TTL: &str = "ttl";
}

pub async fn get_udp_addrs(address: Address<'_>) -> ZResult<impl Iterator<Item = SocketAddr>> {
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30 changes: 29 additions & 1 deletion io/zenoh-links/zenoh-link-udp/src/multicast.rs
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Expand Up @@ -272,7 +272,7 @@ impl LinkManagerMulticastUdp {
.map_err(|e| zerror!("{}: {}", mcast_addr, e))?;
}

// Bind the socket: let's bing to the unspecified address so we can join and read
// Bind the socket: let's bind to the unspecified address so we can join and read
// from multiple multicast groups.
let bind_mcast_addr = match mcast_addr.ip() {
IpAddr::V4(_) => IpAddr::V4(Ipv4Addr::UNSPECIFIED),
Expand Down Expand Up @@ -321,6 +321,34 @@ impl LinkManagerMulticastUdp {
// https://docs.rs/tokio/latest/tokio/net/struct.UdpSocket.html#notes
mcast_sock.set_nonblocking(true)?;

// If TTL is specified, add set the socket's TTL
if let Some(ttl_str) = config.get(UDP_MULTICAST_TTL) {
let ttl = match ttl_str.parse::<u32>() {
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@Mallets Mallets Mar 20, 2025

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IPv6 hop limit is not yet supported in the Rust library.
I've opened rust-lang/rust#138744 to address the issue.

In the meanwhile, I suggest to simply log a warning in the case of an IPv6 socket.

        // If TTL is specified, add set the socket's TTL
        if let Some(ttl_str) = config.get(UDP_MULTICAST_TTL) {
            match &local_addr {
                IpAddr::V4(_) => {
                    let ttl = match ttl_str.parse::<u32>() {
                        Ok(ttl) => ttl,
                        Err(e) => bail!("Can not parse TTL '{}' to a u32: {}", ttl_str, e),
                    };

                    ucast_sock.set_multicast_ttl_v4(ttl).map_err(|e| {
                        zerror!("Can not set multicast TTL {} on {}: {}", ttl, mcast_addr, e)
                    })?;
                }
                IpAddr::V6(_) => {
                    tracing::warn!(
                            "UDP multicast hop limit not supported for v6 socket: {}. See https://github.com/rust-lang/rust/pull/138744.",
                            mcast_addr
                        );
                }
            }
        }

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@jmonticelli jmonticelli Mar 20, 2025

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Wasn't sure how tokio handled this under the hood, I just saw is said it "may not have any effect" and figured it was a shot in the dark to attempt to set the TTL.

Sounds great, I will make this change. Thanks!

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@jmonticelli jmonticelli Mar 20, 2025

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I have taken your changes, feel free to re-review that they were taken correctly.
It passed a local build for me.

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@Mallets Mallets Mar 21, 2025

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All good, thanks!

Ok(ttl) => ttl,
Err(e) => bail!("Can not parse TTL '{}' to a u32: {}", ttl_str, e),
};

match &local_addr {
IpAddr::V4(_) => {
ucast_sock
.set_multicast_ttl_v4(ttl)
.map_err(|e| zerror!("{}: {}", mcast_addr, e))?;
}
IpAddr::V6(_) => match zenoh_util::net::get_index_of_interface(local_addr) {
Ok(_) => {
tracing::warn!(
"set_multicast_ttl_v4 on v6 socket (may have no effect): {}",
mcast_addr
);
ucast_sock
.set_multicast_ttl_v4(ttl)
.map_err(|e| zerror!("{}: {}", mcast_addr, e))?
}
Err(e) => bail!("{}: {}", mcast_addr, e),
},
}
}

// Build the tokio multicast UdpSocket
let mcast_sock = UdpSocket::from_std(mcast_sock.into())?;

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