1 files changed, 186 insertions, 0 deletions
diff --git a/src/linux/routes.rs b/src/linux/routes.rs
new file mode 100644
index 0000000..07083bb
--- /dev/null
+++ b/src/linux/routes.rs
@@ -0,0 +1,186 @@
+use super::firewall::CAPTURE_MARK;
+use anyhow::{Result, ensure};
+use futures_util::TryStreamExt;
+use rtnetlink::{
+    Handle, IpVersion, RouteMessageBuilder,
+    packet_route::{
+        route::{RouteAttribute, RouteProtocol},
+        rule::{RuleAction, RuleAttribute},
+    },
+};
+use std::net::{Ipv4Addr, Ipv6Addr};
+
+const TABLE_ID: u32 = 20260;
+const PRIORITY: u32 = 10260;
+const PROTOCOL: u8 = 186;
+
+fn connection() -> Result<Handle> {
+    let (connection, handle, _) = rtnetlink::new_connection()?;
+    tokio::spawn(connection);
+    Ok(handle)
+}
+
+pub async fn preflight() -> Result<()> {
+    let handle = connection()?;
+    for version in [IpVersion::V4, IpVersion::V6] {
+        let mut rules = handle.rule().get(version).execute();
+        while let Some(rule) = rules.try_next().await? {
+            let priority = rule
+                .attributes
+                .iter()
+                .find_map(|a| {
+                    if let RuleAttribute::Priority(v) = a {
+                        Some(*v)
+                    } else {
+                        None
+                    }
+                })
+                .unwrap_or(0);
+            ensure!(
+                matches!(priority, 0 | 32766 | 32767) || owned_rule(&rule),
+                "Unsupported policy-routing rule at priority {}; remove conflicting VPN or policy routing before enabling",
+                priority
+            );
+        }
+    }
+    let mut routes = handle
+        .route()
+        .get(rtnetlink::RouteMessageBuilder::<std::net::IpAddr>::new().build())
+        .execute();
+    while let Some(route) = routes.try_next().await? {
+        if table(&route) == TABLE_ID {
+            ensure!(
+                route.header.protocol == RouteProtocol::Other(PROTOCOL),
+                "Roentgen route table is already in use"
+            );
+        }
+    }
+    Ok(())
+}
+
+fn table(route: &rtnetlink::packet_route::route::RouteMessage) -> u32 {
+    route
+        .attributes
+        .iter()
+        .find_map(|a| {
+            if let RouteAttribute::Table(v) = a {
+                Some(*v)
+            } else {
+                None
+            }
+        })
+        .unwrap_or(u32::from(route.header.table))
+}
+fn owned_rule(rule: &rtnetlink::packet_route::rule::RuleMessage) -> bool {
+    rule.attributes.contains(&RuleAttribute::Priority(PRIORITY))
+        && rule
+            .attributes
+            .contains(&RuleAttribute::FwMark(CAPTURE_MARK))
+        && rule
+            .attributes
+            .contains(&RuleAttribute::FwMask(CAPTURE_MARK))
+        && rule.attributes.contains(&RuleAttribute::Table(TABLE_ID))
+        && rule.header.action == RuleAction::ToTable
+}
+
+pub async fn capture(interface: u32) -> Result<()> {
+    let handle = connection()?;
+    for route in [
+        RouteMessageBuilder::<Ipv4Addr>::new()
+            .table_id(TABLE_ID)
+            .output_interface(interface)
+            .protocol(RouteProtocol::Other(PROTOCOL))
+            .build(),
+        RouteMessageBuilder::<Ipv6Addr>::new()
+            .table_id(TABLE_ID)
+            .output_interface(interface)
+            .protocol(RouteProtocol::Other(PROTOCOL))
+            .build(),
+    ] {
+        handle.route().add(route).replace().execute().await?;
+    }
+    for version in [IpVersion::V4, IpVersion::V6] {
+        let existing: Vec<_> = handle
+            .rule()
+            .get(version.clone())
+            .execute()
+            .try_collect()
+            .await?;
+        if existing.iter().any(owned_rule) {
+            continue;
+        }
+        match version {
+            IpVersion::V4 => {
+                let mut request = handle
+                    .rule()
+                    .add()
+                    .v4()
+                    .priority(PRIORITY)
+                    .table_id(TABLE_ID)
+                    .fw_mark(CAPTURE_MARK)
+                    .action(RuleAction::ToTable);
+                request
+                    .message_mut()
+                    .attributes
+                    .push(RuleAttribute::FwMask(CAPTURE_MARK));
+                request.execute().await?;
+            }
+            IpVersion::V6 => {
+                let mut request = handle
+                    .rule()
+                    .add()
+                    .v6()
+                    .priority(PRIORITY)
+                    .table_id(TABLE_ID)
+                    .fw_mark(CAPTURE_MARK)
+                    .action(RuleAction::ToTable);
+                request
+                    .message_mut()
+                    .attributes
+                    .push(RuleAttribute::FwMask(CAPTURE_MARK));
+                request.execute().await?;
+            }
+        }
+    }
+    Ok(())
+}
+
+pub async fn remove() -> Result<()> {
+    let handle = connection()?;
+    for version in [IpVersion::V4, IpVersion::V6] {
+        let rules: Vec<_> = handle
+            .rule()
+            .get(version.clone())
+            .execute()
+            .try_collect()
+            .await?;
+        for rule in rules.into_iter().filter(owned_rule) {
+            handle.rule().del(rule).execute().await?;
+        }
+    }
+    let routes: Vec<_> = handle
+        .route()
+        .get(RouteMessageBuilder::<std::net::IpAddr>::new().build())
+        .execute()
+        .try_collect()
+        .await?;
+    for route in routes
+        .into_iter()
+        .filter(|r| table(r) == TABLE_ID && r.header.protocol == RouteProtocol::Other(PROTOCOL))
+    {
+        handle.route().del(route).execute().await?;
+    }
+    Ok(())
+}
+
+pub async fn tun_index() -> Result<Option<u32>> {
+    let handle = connection()?;
+    Ok(handle
+        .link()
+        .get()
+        .match_name("roentgen0")
+        .execute()
+        .try_next()
+        .await?
+        .map(|link| link.header.index))
+}