feat(iroh)!: allow multiple IP transports, including filtering by interface by dignifiedquire · Pull Request #3692 · n0-computer/iroh

dignifiedquire · 2025-11-22T08:56:49Z

Description

This allows for multiple interfaces to be bound, and be actually used.

You can now use this by passing

let endpoint = Endpoint::builder()
    .bind_addr("127.0.0.1:1234")?
    .bind_addr_with_opts("192.168.1.2:1234", BindOpts::default().set_prefix_len(24))?
    .bind()
    .await?

The selection of the interface is done internally by first looking at all specific bindings, and then fallbing back to the default version for this family.

Closes #3218

Breaking Changes

iroh
- removed
  - Endpoint::bind_addr_v4
  - Endpoint::bind_addr_v6
- added
  - Endpoint::bind_addr
  - Endpoint::bind_addr_with_opts
  - endpoint::BindOpts
  - endpoint::ToSocketAddr

github-actions · 2025-11-22T08:59:36Z

Documentation for this PR has been generated and is available at: https://n0-computer.github.io/iroh/pr/3692/docs/iroh/

Last updated: 2026-01-08T19:59:29Z

github-actions · 2025-11-22T09:03:39Z

Netsim report & logs for this PR have been generated and is available at: LOGS
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Last updated for commit: 5d84dd8

Frando · 2025-12-19T12:18:26Z

We could remove the _default API I think, if you set a netmask of 0 it will apply to everything. And instead return an error if you bind conflicting networks.

dignifiedquire · 2025-12-19T12:59:43Z

We could remove the _default API I think, if you set a netmask of 0 it will apply to everything. And instead return an error if you bind conflicting networks.

well currently they are treated differently internally as an explicit fallback, thats why the difference in configuration exists

iroh/src/magicsock/transports.rs

matheus23

I'm not super convinced this is the right API 🤔

Looking at your example:

let endpoint = Endpoint::builder()
  .bind_addr_v4_default("127.0.0.1", 1234)
  .bind_addr_v4("192.168.1.2/24".parse()?, 1234) // bind to prefix_len of 24
  .bind()
  .await?

It looks like the configuration for an endpoint that will only send traffic in the local network and localhost.
So let's say quinn produces a datagram that's meant to be sent to 192.168.1.101:1234.
Iroh will then first check this against your 192.168.1.2/24 and find a match. However, it turns out that interface is actually busy, so it continues.
Then it'll see the "default" 127.0.0.1 interface and try to send on that. But obviously it can't send outside localhost, so ideally that should just fail sending, but I think it won't? I'm not actually sure what will happen.

Also another thing about the default socket: What if someone wants to bind a dual-stack socket with [::]? I think that should match against an IPv4 address, but IIUC currently it doesn't?

Minor note: I'm not sure what should happen if you bind multiple sockets to the same port, but different IP addrs. What happens in these cases? I'm not sure.

iroh/src/magicsock/transports/ip.rs

dignifiedquire · 2026-01-07T10:41:37Z

What if someone wants to bind a dual-stack socket

We don't support dual socket, not currently, and not in this setup

flub

hitting the "submit review" button to get the routing comments out

flub · 2026-01-08T10:08:54Z

iroh/src/endpoint/bind.rs

+    ///
+    /// Defaults to `0`.
+    ///
+    /// Must not be larger than `32`


This isn't used for IPv6 addresses? There they go up to /64 or /128 even.

Maybe you don't even really need a limit, if the netmask is larger then the address it is the equivalent of the netmask of all ones after all.

fixed already

flub · 2026-01-08T10:30:02Z

iroh/src/magicsock/transports/ip.rs

+/// IP transport configuration
+#[derive(Debug, Copy, Clone, PartialEq, Eq)]
+pub enum Config {
+    /// Default IPv4 binding


Needs to elaborate what "default" means here. I assume it means that this will be the default route for initiated outgoing packets that don't match the subnet of any other bind.

I do think splitting V4 anv V4Default here is logically a bit wrong. Because each bound socket bound on a specific local interface does have the subnet of that interface, regardless of whether it is used as default if no subnets match or not. So I'd rather have an is_default in the fields of V4 & V6.

So I'd rather have an is_default in the fields of V4 & V6.

they store different information at this point, which is why they are different enum variants

I think what @flub is suggesting is removing Config::V*Default cases, and adding an is_default: bool.
And then representing e.g. Config::V4Default { ip_addr: "0.0.0.0".parse()?, port: 1234, is_required: true } as
Config::V4 { ip_net: "0.0.0.0/0".parse()?, port: 1234, is_required: true, is_default: true }.

So, in short, representing the old default case as having prefix len 0.

iroh/src/endpoint/bind.rs

iroh/src/magicsock/transports/ip.rs

flub · 2026-01-08T10:47:25Z

iroh/src/magicsock/transports/ip.rs

+    /// General IPv4 binding
+    V4 {
+        /// The IP address to bind on
+        ip_addr: Ipv4Net,


nit, call this field ip_net or even net. This also shows up in the functions where you use this where it's suddenly confusing to read ip_addr.add() or ip_addr.contains(an_actual_ip_addr).

flub · 2026-01-08T10:54:07Z

iroh/src/magicsock/transports/ip.rs

-        let socket = bind_with_fallback(bind_addr)?;
-        Ok(Self::new(bind_addr, Arc::new(socket), metrics.clone()))
+    pub(crate) fn bind(config: Config, metrics: Arc<MagicsockMetrics>) -> io::Result<Self> {
+        let socket = bind_with_fallback(config.into())?;


I find this very surprising that someone passed in a Config with a specific port but it will now potentially ignore this port. For folks who configure things accurately this is bad behaviour.

this has been the behaviour for a long time, so changing this should be a separate discussion imho

It has been the default for a long time and when users notice it has been really surprising to them!

The API we're adding is explicitly to give more control over what is exactly bound. I think this should also be exposed in a BindOpts field so that you get control over it. And by default this should be set to not fallback as otherwise this will be very surprising to users.

If a user does not manually call any Builder::bind_addr* functions then setting that bind option to use the fallback on the two IP transports added in that case is reasonable.

will do this change in a follow up

flub · 2026-01-08T11:03:43Z

iroh/src/magicsock/transports/ip.rs

+                }
+            };
+        }
+


IIUC if we are CPU bound and can not keep up we'll prefer v4_default, then v4, then v6_default and then v6. I guess that's fine for now, but could we leave a TODO or some comment that this bias exists?

iroh/src/magicsock/transports/ip.rs

iroh/src/magicsock/transports.rs

iroh/src/endpoint.rs

flub · 2026-01-08T12:46:24Z

iroh/src/endpoint.rs

+    ///
+    /// Only a single interface can be the default, per IP family, so this errors out if one is already set.
+    ///
+    /// If you want to remove the default transports, make sure to call `clear_ip` first.


How empty is a Buidler::empty_builder? I think right now it still includes these default binds, which honestly is a bit confusing.

Also, having to call clear_ip is quite the footgun. I think it would be more logical from the user's view if we always created a builder without any pre-configured binds. And only if the user did not call any bind_addr* method before calling Builder::bind then add the IPv4 UNSPECIFIED and optional IPv6 UNSPECIFIED binds.

And only if the user did not call any bind_addr* method before calling Builder::bind then add the IPv4 UNSPECIFIED and optional IPv6 UNSPECIFIED binds.

I tried that, that doesn't work, as we have a test and use case for not having any IP transport already

Also, having to call clear_ip is quite the footgun

we have it for other things like discovery, and it really is needed to make sure for example things from presets are removed

How empty is a Buidler::empty_builder? I think right now it still includes these default binds, which honestly is a bit confusing.

it is as empty as we can make it, while still being able to do something when starting it

we could make it fully empty, and add the default binds using the n0 preset

Consider that today you can call clear_relay_transport and then you can not add a relay transport back (you can only add a relay transport by using Builder::empty(RelayMode)) I would propose to rename clear_relay_transport and clear_ip_transport into disable_*_transport and then this is solved.

iroh/src/magicsock/transports.rs

matheus23

Yay routing tables and interfaces.

The "default_ipv{4,6}" I commented on can be ignored. "Default" here is an overloaded term. It's fine to keep it as is (it's not public API, we can improve it later)

iroh/src/endpoint/bind.rs

iroh/src/magicsock/transports/ip.rs

## Description The new user-defined IP transports added #3692 don't actually work because they are filtered out in `Transports::bind`. Here's a fix, and a test that tests the currently implemented behavior. The test fails without this fix. ## Breaking Changes  ## Notes & open questions  ## Change checklist  - [ ] Self-review. - [ ] Documentation updates following the [style guide](https://rust-lang.github.io/rfcs/1574-more-api-documentation-conventions.html#appendix-a-full-conventions-text), if relevant. - [ ] Tests if relevant. - [ ] All breaking changes documented. - [ ] List all breaking changes in the above "Breaking Changes" section. - [ ] Open an issue or PR on any number0 repos that are affected by this breaking change. Give guidance on how the updates should be handled or do the actual updates themselves. The major ones are: - [ ] [`quic-rpc`](https://github.com/n0-computer/quic-rpc) - [ ] [`iroh-gossip`](https://github.com/n0-computer/iroh-gossip) - [ ] [`iroh-blobs`](https://github.com/n0-computer/iroh-blobs) - [ ] [`dumbpipe`](https://github.com/n0-computer/dumbpipe) - [ ] [`sendme`](https://github.com/n0-computer/sendme)

n0bot bot added this to iroh Nov 22, 2025

github-project-automation bot moved this to 🏗 In progress in iroh Nov 22, 2025

dignifiedquire marked this pull request as ready for review November 22, 2025 13:46

dignifiedquire changed the title ~~feat(iroh): allow IP transports to bind to multiple interfaces~~ feat(iroh)!: allow IP transports to bind to multiple interfaces Nov 22, 2025

dignifiedquire changed the title ~~feat(iroh)!: allow IP transports to bind to multiple interfaces~~ feat(iroh)!: allow multiple IP transports, including filtering by interface Nov 22, 2025

dignifiedquire force-pushed the feat-bind-interfaces branch 2 times, most recently from 6726f3c to 479652f Compare November 25, 2025 10:13

dignifiedquire and others added 8 commits November 28, 2025 12:57

feat(iroh): allow IP transports to bind to multiple interfaces

00c7d67

fix: restructure ip transports

c0cfa7b

cleanup structure

6e4c785

cleanup code some more

3978f6b

fixup address mapping

262a3d2

example: expand transfer.rs example to support explicit interface binds

0c1c3a1

cleanup

b5ff035

cleanup

232524f

dignifiedquire force-pushed the feat-bind-interfaces branch from 479652f to 232524f Compare November 28, 2025 12:00

rklaehn and others added 3 commits December 10, 2025 18:09

Merge branch 'feat-multipath' into feat-bind-interfaces

48e256c

Merge remote-tracking branch 'origin/main' into feat-bind-interfaces

e7345b3

cleanup

b6659c9

dignifiedquire requested a review from ramfox December 19, 2025 10:39

dignifiedquire changed the base branch from feat-multipath to main December 19, 2025 10:39

matheus23 reviewed Dec 19, 2025

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flub added this to the iroh: v1.0.0-rc.0 milestone Dec 22, 2025

improve docs and fix initial default overrides

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dignifiedquire added 2 commits January 8, 2026 16:14

implement is_default setting based on @flub CR

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cleanup poll_send logic

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dignifiedquire mentioned this pull request Jan 8, 2026

refactor: clean up is_user_defined logic #3831

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dignifiedquire added 3 commits January 8, 2026 16:57

fixup wasm

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Merge remote-tracking branch 'origin/main' into feat-bind-interfaces

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set scope_ids to 0

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detect ipv6 support in tests

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dignifiedquire and others added 5 commits January 8, 2026 17:43

apply docs from @flub

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more CR

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rename to is_default_route

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Merge remote-tracking branch 'origin/main' into feat-bind-interfaces

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Doc comments for the Endpoing::bind_addr functions

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Merged via the queue into main with commit 2359acf Jan 8, 2026
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github-project-automation bot moved this from 👀 In review to ✅ Done in iroh Jan 8, 2026

matheus23 deleted the feat-bind-interfaces branch January 9, 2026 08:07

Frando mentioned this pull request Jan 9, 2026

fix(iroh): actually use user-provided bind addrs #3835

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