Support ip route get

[hack3ric]

Rework of #23. Only adds RouteGetRequest::dump option, where specifying req.dump(false) will mimic the behaviour of ip route get, and replacing impl TryStream with impl Stream<Item = Result<...>>. There is no breaking change.

[nhed]

Any idea bout the status f this PR?
I need ip route get functionality and hacked out the dump locally.

[hack3ric]

Seems the maintainer has been inactive for some time on this repo, so we have to either wait or fork.

[nhed]

not sure if valuable - but as an alternate to adding a dump variable at construction time I thought it might make sense to drive this behavior by the presence of a destination attribute.

If destination attribute was added (as one would have to to obtain a route) user is looking for a single route
otherwise - dump all the routes

diff --git a/src/route/get.rs b/src/route/get.rs
index a938532..68f27bf 100644
--- a/src/route/get.rs
+++ b/src/route/get.rs
@@ -11,7 +11,7 @@ use netlink_packet_route::{
     route::RouteMessage, AddressFamily, RouteNetlinkMessage,
 };
 
-use crate::{try_rtnl, Error, Handle};
+use crate::{try_rtnl, Error, Handle, packet_route::route::RouteAttribute};
 
 pub struct RouteGetRequest {
     handle: Handle,
@@ -51,9 +51,14 @@ impl RouteGetRequest {
             message,
         } = self;
 
+        let has_dest = message.attributes.iter().any(|attr| match attr {
+            RouteAttribute::Destination(_) => true,
+            _ => false,
+        });
+
         let mut req =
             NetlinkMessage::from(RouteNetlinkMessage::GetRoute(message));
-        req.header.flags = NLM_F_REQUEST | NLM_F_DUMP;
+        req.header.flags = NLM_F_REQUEST | if has_dest { 0 } else { NLM_F_DUMP };
 
         match handle.request(req) {
             Ok(response) => Either::Left(response.map(move |msg| {

---

edit: slightly cleaner version of ^^

diff --git a/src/route/get.rs b/src/route/get.rs
index a938532..3e61f29 100644
--- a/src/route/get.rs
+++ b/src/route/get.rs
@@ -11,7 +11,7 @@ use netlink_packet_route::{
     route::RouteMessage, AddressFamily, RouteNetlinkMessage,
 };
 
-use crate::{try_rtnl, Error, Handle};
+use crate::{packet_route::route::RouteAttribute, try_rtnl, Error, Handle};
 
 pub struct RouteGetRequest {
     handle: Handle,
@@ -51,9 +51,18 @@ impl RouteGetRequest {
             message,
         } = self;
 
+        let has_dest = message
+            .attributes
+            .iter()
+            .any(|attr| matches!(attr, RouteAttribute::Destination(_)));
+
         let mut req =
             NetlinkMessage::from(RouteNetlinkMessage::GetRoute(message));
-        req.header.flags = NLM_F_REQUEST | NLM_F_DUMP;
+        req.header.flags = NLM_F_REQUEST;
+
+        if !has_dest {
+            req.header.flags |= NLM_F_DUMP;
+        }
 
         match handle.request(req) {
             Ok(response) => Either::Left(response.map(move |msg| {

[nhed]

My rust is not so great - so I wasn't able to use your fix - so you have an example of how you would modify the existing examples? Reading your commit message I tried this but dump is just a field, not an access method.

+++ b/examples/get_route.rs
@@ -35,7 +35,7 @@ async fn dump_addresses(
         IpVersion::V4 => RouteMessageBuilder::<Ipv4Addr>::new().build(),
         IpVersion::V6 => RouteMessageBuilder::<Ipv6Addr>::new().build(),
     };
-    let mut routes = handle.route().get(route).execute();
+    let mut routes = handle.route().get(route).dump(false).execute();
     while let Some(route) = routes.try_next().await? {
         println!("{route:?}");
     }

yielding

error[E0599]: no method named `dump` found for struct `RouteGetRequest` in the current scope
  --> examples/get_route.rs:38:48
   |
38 |     let mut routes = handle.route().get(route).dump(false).execute();
   |                                                ^^^^ private field, not a method

Feels like one would need to add an access method, might just make my own temporary for till that clears up as the solution I outlined in the prior comment works transparently

[hack3ric]

Oops, seems like I somehow missed .dump() method when cherry-picking from my own branch. Fixed now. Thanks for the review!

If destination attribute was added (as one would have to to obtain a route) user is looking for a single route otherwise - dump all the routes

This definitely seems feasible! I wonder if there are corner cases, though. I will integrate your changes and mention you in the commit message when I am less busy (or create a new PR superseding this one) :)

[nhed]

I will integrate your changes

if you do please note i updated my comment with slightly cleaner code