Refactor server resolution

src/api/server_server.rs

@@ -70,9 +70,10 @@ use crate::{
     Ar, Error, PduEvent, Ra, Result,
 };
 
+pub(crate) mod resolution;
 mod send_request;
 
-pub(crate) use send_request::{send_request, FedDest};
+pub(crate) use send_request::send_request;
 
 /// # `GET /_matrix/federation/v1/version`
 ///

src/api/server_server/resolution.rs

@@ -0,0 +1,366 @@
+use std::{
+    borrow::Cow,
+    fmt::Debug,
+    net::{IpAddr, SocketAddr},
+    str::FromStr,
+};
+
+use ruma::ServerName;
+use thiserror::Error;
+use tracing::{debug, error, warn};
+
+use crate::{services, Result};
+/// Wraps either a literal IP address or a hostname, plus an optional port.
+///
+/// # Examples:
+/// ```rust
+/// # use grapevine::api::server_server::FedDest;
+/// # fn main() -> Result<(), std::net::AddrParseError> {
+/// FedDest::Literal("198.51.100.3:8448".parse()?);
+/// FedDest::Literal("[2001:db8::4:5]:443".parse()?);
+/// FedDest::Named("matrix.example.org".to_owned(), "".to_owned());
+/// FedDest::Named("matrix.example.org".to_owned(), ":8448".to_owned());
+/// FedDest::Named("198.51.100.5".to_owned(), "".to_owned());
+/// # Ok(())
+/// # }
+/// ```
+#[derive(Clone, Debug, PartialEq, Eq)]
+enum FedDest {
+    BareLiteral(IpAddr),
+    PortLiteral(SocketAddr),
+    Named(String, Option<u16>),
+}
+
+impl FedDest {
+    fn host_and_port_or_default(&self) -> (Cow<'_, str>, u16) {
+        const DEFAULT_PORT: u16 = 8448;
+
+        match self {
+            FedDest::BareLiteral(addr) => {
+                (Cow::Owned(addr.to_string()), DEFAULT_PORT)
+            }
+            FedDest::PortLiteral(addr) => {
+                (Cow::Owned(addr.ip().to_string()), addr.port())
+            }
+            FedDest::Named(host, port) => {
+                (Cow::Borrowed(host), port.unwrap_or(DEFAULT_PORT))
+            }
+        }
+    }
+}
+
+#[derive(Debug, Error)]
+enum InvalidFedDest {
+    #[error("invalid port {0}")]
+    InvalidPort(String),
+}
+
+impl FromStr for FedDest {
+    type Err = InvalidFedDest;
+
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        if let Ok(destination) = s.parse::<SocketAddr>() {
+            Ok(FedDest::PortLiteral(destination))
+        } else if let Ok(ip_addr) = s.parse::<IpAddr>() {
+            Ok(FedDest::BareLiteral(ip_addr))
+        } else if let Some((host, port)) = s.split_once(':') {
+            Ok(FedDest::Named(
+                host.to_owned(),
+                Some(port.parse().map_err(|_| {
+                    InvalidFedDest::InvalidPort(port.to_owned())
+                })?),
+            ))
+        } else {
+            Ok(FedDest::Named(s.to_owned(), None))
+        }
+    }
+}
+
+#[derive(Debug, Clone)]
+enum WellKnownResult {
+    Success {
+        delegated_dest: FedDest,
+    },
+    Error,
+}
+
+#[derive(Debug, Clone)]
+enum SrvResult {
+    Success {
+        host: String,
+        port: u16,
+    },
+    Error,
+}
+
+#[derive(Debug, Clone)]
+struct LookupResult {
+    well_known: WellKnownResult,
+    srv: Option<SrvResult>,
+}
+
+#[derive(Debug, Clone)]
+pub(crate) struct ResolutionResult {
+    original: FedDest,
+    // None if `original` is an IP literal or has a port (used as-is)
+    lookup: Option<LookupResult>,
+}
+
+impl ResolutionResult {
+    pub(crate) fn host_header(&self) -> String {
+        let dest = match &self.lookup {
+            None
+            | Some(LookupResult {
+                well_known: WellKnownResult::Error,
+                ..
+            }) => {
+                // no lookup performed or well-known lookup failed
+                &self.original
+            }
+
+            Some(LookupResult {
+                well_known:
+                    WellKnownResult::Success {
+                        delegated_dest,
+                    },
+                ..
+            }) => {
+                // well-known lookup succeeded
+                delegated_dest
+            }
+        };
+
+        match dest {
+            FedDest::BareLiteral(addr) => format!("{addr}"),
+            FedDest::PortLiteral(addr) => format!("{addr}"),
+            FedDest::Named(host, port) => {
+                if let Some(port) = port {
+                    format!("{host}:{port}")
+                } else {
+                    host.clone()
+                }
+            }
+        }
+    }
+
+    pub(crate) fn base_url(&self) -> String {
+        let (host, port) = match &self.lookup {
+            None
+            | Some(LookupResult {
+                well_known: WellKnownResult::Error,
+                srv: None | Some(SrvResult::Error),
+            }) => {
+                // all lookups failed, or no lookups were performed
+                self.original.host_and_port_or_default()
+            }
+
+            Some(LookupResult {
+                well_known:
+                    WellKnownResult::Success {
+                        delegated_dest,
+                    },
+                srv: None | Some(SrvResult::Error),
+            }) => {
+                // SRV lookup failed, but well-known lookup succeeded
+                delegated_dest.host_and_port_or_default()
+            }
+
+            Some(LookupResult {
+                srv:
+                    Some(SrvResult::Success {
+                        host,
+                        port,
+                    }),
+                ..
+            }) => {
+                // SRV lookup succeeded (result of well-known lookup isn't
+                // relevant)
+                (Cow::Borrowed(host.as_str()), *port)
+            }
+        };
+
+        format!("https://{host}:{port}")
+    }
+}
+
+/// Returns: `actual_destination`, `Host` header
+/// Implemented according to the specification at <https://matrix.org/docs/spec/server_server/r0.1.4#resolving-server-names>
+/// Numbers in comments below refer to bullet points in linked section of
+/// specification
+#[allow(clippy::too_many_lines)]
+#[tracing::instrument(ret(level = "debug"))]
+pub(crate) async fn find_actual_destination(
+    destination: &'_ ServerName,
+) -> ResolutionResult {
+    let original: FedDest = destination
+        .as_str()
+        .parse()
+        .expect("ServerName should always be a valid FedDest");
+
+    let hostname = match &original {
+        FedDest::BareLiteral(_) | FedDest::PortLiteral(_) => {
+            debug!("1: IP literal");
+            return ResolutionResult {
+                original,
+                lookup: None,
+            };
+        }
+        FedDest::Named(_, Some(_)) => {
+            debug!("2: Hostname with port");
+            return ResolutionResult {
+                original,
+                lookup: None,
+            };
+        }
+        FedDest::Named(host, None) => host,
+    };
+
+    debug!("Requesting .well-known");
+    let well_known_error = 'well_known: {
+        let Some(delegated_hostname) = request_well_known(hostname).await
+        else {
+            debug!("Invalid/failed .well-known response");
+            break 'well_known WellKnownResult::Error;
+        };
+        let Ok(delegated_dest) = delegated_hostname.parse() else {
+            debug!("Malformed delegation in .well-known");
+            break 'well_known WellKnownResult::Error;
+        };
+
+        debug!("3: A .well-known file is available");
+
+        let srv = match &delegated_dest {
+            FedDest::BareLiteral(_) | FedDest::PortLiteral(_) => {
+                debug!("3.1: IP literal in .well-known file");
+
+                None
+            }
+            FedDest::Named(_, Some(_)) => {
+                debug!("3.2: Hostname with port in .well-known file");
+
+                None
+            }
+            FedDest::Named(delegated_hostname, None) => {
+                let srv = query_and_store_srv_record(delegated_hostname).await;
+                if let SrvResult::Success {
+                    ..
+                } = &srv
+                {
+                    debug!(
+                        "3.3/3.4: SRV lookup of delegated destination \
+                         successful"
+                    );
+                } else {
+                    debug!(
+                        "3.5: SRV lookup failed, using delegated destination"
+                    );
+                }
+
+                Some(srv)
+            }
+        };
+
+        return ResolutionResult {
+            original,
+            lookup: Some(LookupResult {
+                well_known: WellKnownResult::Success {
+                    delegated_dest,
+                },
+                srv,
+            }),
+        };
+    };
+
+    let srv = query_and_store_srv_record(hostname).await;
+    if let SrvResult::Success {
+        ..
+    } = &srv
+    {
+        debug!("4/5: SRV lookup of original destination successful");
+    } else {
+        debug!("6: SRV lookup failed, using original destination");
+    }
+
+    ResolutionResult {
+        original,
+        lookup: Some(LookupResult {
+            well_known: well_known_error,
+            srv: Some(srv),
+        }),
+    }
+}
+
+#[tracing::instrument(ret(level = "debug"))]
+async fn query_given_srv_record(record: &str) -> SrvResult {
+    services()
+        .globals
+        .dns_resolver()
+        .srv_lookup(record)
+        .await
+        .ok()
+        .and_then(|srv| {
+            srv.iter().next().map(|result| SrvResult::Success {
+                host: result
+                    .target()
+                    .to_string()
+                    .trim_end_matches('.')
+                    .to_owned(),
+                port: result.port(),
+            })
+        })
+        .unwrap_or(SrvResult::Error)
+}
+
+#[tracing::instrument(ret(level = "debug"))]
+async fn query_and_store_srv_record(hostname: &'_ str) -> SrvResult {
+    let hostname = hostname.trim_end_matches('.');
+
+    let mut result =
+        query_given_srv_record(&format!("_matrix-fed._tcp.{hostname}.")).await;
+    if matches!(result, SrvResult::Error) {
+        result =
+            query_given_srv_record(&format!("_matrix._tcp.{hostname}.")).await;
+    }
+
+    let SrvResult::Success {
+        host,
+        port,
+    } = &result
+    else {
+        return result;
+    };
+
+    if let Ok(override_ip) =
+        services().globals.dns_resolver().lookup_ip(host).await
+    {
+        services()
+            .globals
+            .tls_name_override
+            .write()
+            .unwrap()
+            .insert(hostname.to_owned(), (override_ip.iter().collect(), *port));
+    } else {
+        warn!("Using SRV record, but could not resolve to IP");
+    }
+
+    result
+}
+
+#[tracing::instrument(ret(level = "debug"))]
+async fn request_well_known(destination: &str) -> Option<String> {
+    let response = services()
+        .globals
+        .default_client()
+        .get(&format!("https://{destination}/.well-known/matrix/server"))
+        .send()
+        .await;
+    debug!("Got well known response");
+    if let Err(e) = &response {
+        debug!("Well known error: {e:?}");
+        return None;
+    }
+    let text = response.ok()?.text().await;
+    debug!("Got well known response text");
+    let body: serde_json::Value = serde_json::from_str(&text.ok()?).ok()?;
+    Some(body.get("m.server")?.as_str()?.to_owned())
+}

src/api/server_server/send_request.rs

@@ -1,8 +1,4 @@
-use std::{
-    fmt::Debug,
-    mem,
-    net::{IpAddr, SocketAddr},
-};
+use std::{fmt::Debug, mem};
 
 use axum_extra::headers::{Authorization, HeaderMapExt};
 use bytes::Bytes;
@@ -18,6 +14,7 @@ use ruma::{
 use thiserror::Error;
 use tracing::{debug, error, field, warn};
 
+use super::resolution::find_actual_destination;
 use crate::{
     observability::{FoundIn, Lookup, METRICS},
     services,
@@ -25,62 +22,6 @@ use crate::{
     Error, Result,
 };
 
-/// Wraps either an literal IP address plus port, or a hostname plus complement
-/// (colon-plus-port if it was specified).
-///
-/// Note: A [`FedDest::Named`] might contain an IP address in string form if
-/// there was no port specified to construct a [`SocketAddr`] with.
-///
-/// # Examples:
-/// ```rust
-/// # use grapevine::api::server_server::FedDest;
-/// # fn main() -> Result<(), std::net::AddrParseError> {
-/// FedDest::Literal("198.51.100.3:8448".parse()?);
-/// FedDest::Literal("[2001:db8::4:5]:443".parse()?);
-/// FedDest::Named("matrix.example.org".to_owned(), "".to_owned());
-/// FedDest::Named("matrix.example.org".to_owned(), ":8448".to_owned());
-/// FedDest::Named("198.51.100.5".to_owned(), "".to_owned());
-/// # Ok(())
-/// # }
-/// ```
-#[derive(Clone, Debug, PartialEq, Eq)]
-pub(crate) enum FedDest {
-    Literal(SocketAddr),
-    Named(String, String),
-}
-
-impl FedDest {
-    fn to_https_string(&self) -> String {
-        match self {
-            Self::Literal(addr) => format!("https://{addr}"),
-            Self::Named(host, port) => format!("https://{host}{port}"),
-        }
-    }
-
-    fn to_uri_string(&self) -> String {
-        match self {
-            Self::Literal(addr) => addr.to_string(),
-            Self::Named(host, port) => format!("{host}{port}"),
-        }
-    }
-
-    fn hostname(&self) -> String {
-        match &self {
-            Self::Literal(addr) => addr.ip().to_string(),
-            Self::Named(host, _) => host.clone(),
-        }
-    }
-
-    fn port(&self) -> Option<u16> {
-        match &self {
-            Self::Literal(addr) => Some(addr.port()),
-            Self::Named(_, port) => {
-                port.strip_prefix(':').and_then(|x| x.parse().ok())
-            }
-        }
-    }
-}
-
 #[derive(Debug, Error)]
 enum RequestSignError {
     #[error("invalid JSON in request body")]
@@ -258,29 +199,27 @@ where
         .get(destination)
         .cloned();
 
-    let (actual_destination, host) = if let Some(result) = cached_result {
+    let resolution = if let Some(result) = cached_result {
         METRICS.record_lookup(Lookup::FederationDestination, FoundIn::Cache);
         result
     } else {
         write_destination_to_cache = true;
 
-        let result = find_actual_destination(destination).await;
-
-        (result.0, result.1.to_uri_string())
+        find_actual_destination(destination).await
     };
 
-    let actual_destination_str = actual_destination.to_https_string();
+    let base_url = resolution.base_url();
 
     let http_request = request
         .try_into_http_request::<Vec<u8>>(
-            &actual_destination_str,
+            &base_url,
             SendAccessToken::IfRequired(""),
             &[MatrixVersion::V1_11],
         )
         .map_err(|error| {
             warn!(
                 %error,
-                actual_destination = actual_destination_str,
+                base_url,
                 "Failed to serialize request",
             );
             Error::BadServerResponse("Invalid request")
@@ -298,10 +237,12 @@ where
     let response = T::IncomingResponse::try_from_http_response(http_response);
     if response.is_ok() && write_destination_to_cache {
         METRICS.record_lookup(Lookup::FederationDestination, FoundIn::Remote);
-        services().globals.actual_destination_cache.write().await.insert(
-            OwnedServerName::from(destination),
-            (actual_destination, host),
-        );
+        services()
+            .globals
+            .actual_destination_cache
+            .write()
+            .await
+            .insert(OwnedServerName::from(destination), resolution);
     }
 
     response.map_err(|e| {
@@ -309,269 +250,3 @@ where
         Error::BadServerResponse("Server returned bad 200 response.")
     })
 }
-
-fn get_ip_with_port(destination_str: &str) -> Option<FedDest> {
-    if let Ok(destination) = destination_str.parse::<SocketAddr>() {
-        Some(FedDest::Literal(destination))
-    } else if let Ok(ip_addr) = destination_str.parse::<IpAddr>() {
-        Some(FedDest::Literal(SocketAddr::new(ip_addr, 8448)))
-    } else {
-        None
-    }
-}
-
-fn add_port_to_hostname(destination_str: &str) -> FedDest {
-    let (host, port) = match destination_str.find(':') {
-        None => (destination_str, ":8448"),
-        Some(pos) => destination_str.split_at(pos),
-    };
-    FedDest::Named(host.to_owned(), port.to_owned())
-}
-
-/// Returns: `actual_destination`, `Host` header
-/// Implemented according to the specification at <https://matrix.org/docs/spec/server_server/r0.1.4#resolving-server-names>
-/// Numbers in comments below refer to bullet points in linked section of
-/// specification
-#[allow(clippy::too_many_lines)]
-#[tracing::instrument(ret(level = "debug"))]
-async fn find_actual_destination(
-    destination: &'_ ServerName,
-) -> (FedDest, FedDest) {
-    debug!("Finding actual destination");
-    let destination_str = destination.as_str().to_owned();
-    let mut hostname = destination_str.clone();
-    let actual_destination = match get_ip_with_port(&destination_str) {
-        Some(host_port) => {
-            debug!("1: IP literal with provided or default port");
-            host_port
-        }
-        None => {
-            if let Some(pos) = destination_str.find(':') {
-                debug!("2: Hostname with included port");
-                let (host, port) = destination_str.split_at(pos);
-                FedDest::Named(host.to_owned(), port.to_owned())
-            } else {
-                debug!(%destination, "Requesting well known");
-                if let Some(delegated_hostname) =
-                    request_well_known(destination.as_str()).await
-                {
-                    debug!("3: A .well-known file is available");
-                    hostname = add_port_to_hostname(&delegated_hostname)
-                        .to_uri_string();
-                    if let Some(host_and_port) =
-                        get_ip_with_port(&delegated_hostname)
-                    {
-                        host_and_port
-                    } else if let Some(pos) = delegated_hostname.find(':') {
-                        debug!("3.2: Hostname with port in .well-known file");
-                        let (host, port) = delegated_hostname.split_at(pos);
-                        FedDest::Named(host.to_owned(), port.to_owned())
-                    } else {
-                        debug!("Delegated hostname has no port in this branch");
-                        if let Some(hostname_override) =
-                            query_srv_record(&delegated_hostname).await
-                        {
-                            debug!("3.3: SRV lookup successful");
-                            let force_port = hostname_override.port();
-
-                            if let Ok(override_ip) = services()
-                                .globals
-                                .dns_resolver()
-                                .lookup_ip(hostname_override.hostname())
-                                .await
-                            {
-                                services()
-                                    .globals
-                                    .tls_name_override
-                                    .write()
-                                    .unwrap()
-                                    .insert(
-                                        delegated_hostname.clone(),
-                                        (
-                                            override_ip.iter().collect(),
-                                            force_port.unwrap_or(8448),
-                                        ),
-                                    );
-                            } else {
-                                warn!(
-                                    "Using SRV record, but could not resolve \
-                                     to IP"
-                                );
-                            }
-
-                            if let Some(port) = force_port {
-                                FedDest::Named(
-                                    delegated_hostname,
-                                    format!(":{port}"),
-                                )
-                            } else {
-                                add_port_to_hostname(&delegated_hostname)
-                            }
-                        } else {
-                            debug!(
-                                "3.4: No SRV records, just use the hostname \
-                                 from .well-known"
-                            );
-                            add_port_to_hostname(&delegated_hostname)
-                        }
-                    }
-                } else {
-                    debug!("4: No .well-known or an error occured");
-                    if let Some(hostname_override) =
-                        query_srv_record(&destination_str).await
-                    {
-                        debug!("4: SRV record found");
-                        let force_port = hostname_override.port();
-
-                        if let Ok(override_ip) = services()
-                            .globals
-                            .dns_resolver()
-                            .lookup_ip(hostname_override.hostname())
-                            .await
-                        {
-                            services()
-                                .globals
-                                .tls_name_override
-                                .write()
-                                .unwrap()
-                                .insert(
-                                    hostname.clone(),
-                                    (
-                                        override_ip.iter().collect(),
-                                        force_port.unwrap_or(8448),
-                                    ),
-                                );
-                        } else {
-                            warn!(
-                                "Using SRV record, but could not resolve to IP"
-                            );
-                        }
-
-                        if let Some(port) = force_port {
-                            FedDest::Named(hostname.clone(), format!(":{port}"))
-                        } else {
-                            add_port_to_hostname(&hostname)
-                        }
-                    } else {
-                        debug!("5: No SRV record found");
-                        add_port_to_hostname(&destination_str)
-                    }
-                }
-            }
-        }
-    };
-    debug!(?actual_destination, "Resolved actual destination");
-
-    // Can't use get_ip_with_port here because we don't want to add a port
-    // to an IP address if it wasn't specified
-    let hostname = if let Ok(addr) = hostname.parse::<SocketAddr>() {
-        FedDest::Literal(addr)
-    } else if let Ok(addr) = hostname.parse::<IpAddr>() {
-        FedDest::Named(addr.to_string(), ":8448".to_owned())
-    } else if let Some(pos) = hostname.find(':') {
-        let (host, port) = hostname.split_at(pos);
-        FedDest::Named(host.to_owned(), port.to_owned())
-    } else {
-        FedDest::Named(hostname, ":8448".to_owned())
-    };
-    (actual_destination, hostname)
-}
-
-#[tracing::instrument(ret(level = "debug"))]
-async fn query_given_srv_record(record: &str) -> Option<FedDest> {
-    services()
-        .globals
-        .dns_resolver()
-        .srv_lookup(record)
-        .await
-        .map(|srv| {
-            srv.iter().next().map(|result| {
-                FedDest::Named(
-                    result
-                        .target()
-                        .to_string()
-                        .trim_end_matches('.')
-                        .to_owned(),
-                    format!(":{}", result.port()),
-                )
-            })
-        })
-        .unwrap_or(None)
-}
-
-#[tracing::instrument(ret(level = "debug"))]
-async fn query_srv_record(hostname: &'_ str) -> Option<FedDest> {
-    let hostname = hostname.trim_end_matches('.');
-
-    if let Some(host_port) =
-        query_given_srv_record(&format!("_matrix-fed._tcp.{hostname}.")).await
-    {
-        Some(host_port)
-    } else {
-        query_given_srv_record(&format!("_matrix._tcp.{hostname}.")).await
-    }
-}
-
-#[tracing::instrument(ret(level = "debug"))]
-async fn request_well_known(destination: &str) -> Option<String> {
-    let response = services()
-        .globals
-        .default_client()
-        .get(&format!("https://{destination}/.well-known/matrix/server"))
-        .send()
-        .await;
-    debug!("Got well known response");
-    if let Err(error) = &response {
-        debug!(%error, "Failed to request .well-known");
-        return None;
-    }
-    let text = response.ok()?.text().await;
-    debug!("Got well known response text");
-    let body: serde_json::Value = serde_json::from_str(&text.ok()?).ok()?;
-    Some(body.get("m.server")?.as_str()?.to_owned())
-}
-
-#[cfg(test)]
-mod tests {
-    use super::{add_port_to_hostname, get_ip_with_port, FedDest};
-
-    #[test]
-    fn ips_get_default_ports() {
-        assert_eq!(
-            get_ip_with_port("1.1.1.1"),
-            Some(FedDest::Literal("1.1.1.1:8448".parse().unwrap()))
-        );
-        assert_eq!(
-            get_ip_with_port("dead:beef::"),
-            Some(FedDest::Literal("[dead:beef::]:8448".parse().unwrap()))
-        );
-    }
-
-    #[test]
-    fn ips_keep_custom_ports() {
-        assert_eq!(
-            get_ip_with_port("1.1.1.1:1234"),
-            Some(FedDest::Literal("1.1.1.1:1234".parse().unwrap()))
-        );
-        assert_eq!(
-            get_ip_with_port("[dead::beef]:8933"),
-            Some(FedDest::Literal("[dead::beef]:8933".parse().unwrap()))
-        );
-    }
-
-    #[test]
-    fn hostnames_get_default_ports() {
-        assert_eq!(
-            add_port_to_hostname("example.com"),
-            FedDest::Named(String::from("example.com"), String::from(":8448"))
-        );
-    }
-
-    #[test]
-    fn hostnames_keep_custom_ports() {
-        assert_eq!(
-            add_port_to_hostname("example.com:1337"),
-            FedDest::Named(String::from("example.com"), String::from(":1337"))
-        );
-    }
-}

src/service/globals.rs

@@ -33,7 +33,7 @@ use tracing::{error, Instrument};
 use trust_dns_resolver::TokioAsyncResolver;
 
 use crate::{
-    api::server_server::FedDest,
+    api::server_server::resolution::ResolutionResult,
     observability::FilterReloadHandles,
     service::media::MediaFileKey,
     services,
@@ -41,7 +41,7 @@ use crate::{
     Config, Error, Result,
 };
 
-type WellKnownMap = HashMap<OwnedServerName, (FedDest, String)>;
+type WellKnownMap = HashMap<OwnedServerName, ResolutionResult>;
 type TlsNameMap = HashMap<String, (Vec<IpAddr>, u16)>;
 // Time if last failed try, number of failed tries
 type RateLimitState = (Instant, u32);