Add support for binding to local port ranges and retrying on EADDRNOTAVAIL

5 files changed, 286 insertions, 38 deletions

diff --git a/.bleep b/.bleep
index ac4d790..f403528 100644
--- a/.bleep
+++ b/.bleep
@@ -1 +1 @@
-28f94f2a402bbf66341bdac8fa670caf5b7311e9
\ No newline at end of file
+90c70086397a4708a4dadfed6e6915ce6dc33481
\ No newline at end of file
diff --git a/pingora-core/src/connectors/l4.rs b/pingora-core/src/connectors/l4.rs
index 0162034..58bd209 100644
--- a/pingora-core/src/connectors/l4.rs
+++ b/pingora-core/src/connectors/l4.rs
@@ -33,8 +33,59 @@ pub trait Connect: std::fmt::Debug {
     async fn connect(&self, addr: &SocketAddr) -> Result<Stream>;
 }
 
+/// Settings for binding on connect
+#[derive(Clone, Debug, Default)]
+pub struct BindTo {
+    // local ip address
+    pub addr: Option<InetSocketAddr>,
+    // port range
+    port_range: Option<(u16, u16)>,
+    // whether we fallback and try again on bind errors when a port range is set
+    fallback: bool,
+}
+
+impl BindTo {
+    /// Sets the port range we will bind to where the first item in the tuple is the lower bound
+    /// and the second item is the upper bound.
+    ///
+    /// Note this bind option is only supported on Linux since 6.3, this is a no-op on other systems.
+    /// To reset the range, pass a `None` or `Some((0,0))`, more information can be found [here](https://man7.org/linux/man-pages/man7/ip.7.html)
+    pub fn set_port_range(&mut self, range: Option<(u16, u16)>) -> Result<()> {
+        if range.is_none() && self.port_range.is_none() {
+            // nothing to do
+            return Ok(());
+        }
+
+        match range {
+            // 0,0 is valid for resets
+            None | Some((0, 0)) => self.port_range = Some((0, 0)),
+            // set the port range if valid
+            Some((low, high)) if low > 0 && low < high => {
+                self.port_range = Some((low, high));
+            }
+            _ => return Error::e_explain(SocketError, "invalid port range: {range}"),
+        }
+        Ok(())
+    }
+
+    /// Set whether we fallback on no address available if a port range is set
+    pub fn set_fallback(&mut self, fallback: bool) {
+        self.fallback = fallback
+    }
+
+    /// Configured bind port range
+    pub fn port_range(&self) -> Option<(u16, u16)> {
+        self.port_range
+    }
+
+    /// Whether we attempt to fallback on no address available
+    pub fn will_fallback(&self) -> bool {
+        self.fallback && self.port_range.is_some()
+    }
+}
+
 /// Establish a connection (l4) to the given peer using its settings and an optional bind address.
-pub(crate) async fn connect<P>(peer: &P, bind_to: Option<InetSocketAddr>) -> Result<Stream>
+pub(crate) async fn connect<P>(peer: &P, bind_to: Option<BindTo>) -> Result<Stream>
 where
     P: Peer + Send + Sync,
 {
@@ -142,12 +193,8 @@ pub(crate) fn bind_to_random<P: Peer>(
     peer: &P,
     v4_list: &[InetSocketAddr],
     v6_list: &[InetSocketAddr],
-) -> Option<InetSocketAddr> {
-    let selected = peer.get_peer_options().and_then(|o| o.bind_to);
-    if selected.is_some() {
-        return selected;
-    }
-
+) -> Option<BindTo> {
+    // helper function for randomly picking address
     fn bind_to_ips(ips: &[InetSocketAddr]) -> Option<InetSocketAddr> {
         match ips.len() {
             0 => None,
@@ -159,13 +206,31 @@ pub(crate) fn bind_to_random<P: Peer>(
         }
     }
 
-    match peer.address() {
+    let mut bind_to = peer.get_peer_options().and_then(|o| o.bind_to.clone());
+    if bind_to.as_ref().map(|b| b.addr).is_some() {
+        // already have a bind address selected
+        return bind_to;
+    }
+
+    let addr = match peer.address() {
         SocketAddr::Inet(sockaddr) => match sockaddr {
             InetSocketAddr::V4(_) => bind_to_ips(v4_list),
             InetSocketAddr::V6(_) => bind_to_ips(v6_list),
         },
         SocketAddr::Unix(_) => None,
+    };
+
+    if addr.is_some() {
+        if let Some(bind_to) = bind_to.as_mut() {
+            bind_to.addr = addr;
+        } else {
+            bind_to = Some(BindTo {
+                addr,
+                ..Default::default()
+            });
+        }
     }
+    bind_to
 }
 
 use crate::protocols::raw_connect;
@@ -238,16 +303,25 @@ mod tests {
     #[tokio::test]
     async fn test_conn_error_addr_not_avail() {
         let peer = HttpPeer::new("127.0.0.1:121".to_string(), false, "".to_string());
-        let new_session = connect(&peer, Some("192.0.2.2:0".parse().unwrap())).await;
+        let addr = "192.0.2.2:0".parse().ok();
+        let bind_to = BindTo {
+            addr,
+            ..Default::default()
+        };
+        let new_session = connect(&peer, Some(bind_to)).await;
         assert_eq!(new_session.unwrap_err().etype(), &InternalError)
     }
 
     #[tokio::test]
     async fn test_conn_error_other() {
         let peer = HttpPeer::new("240.0.0.1:80".to_string(), false, "".to_string()); // non localhost
-
+        let addr = "127.0.0.1:0".parse().ok();
         // create an error: cannot send from src addr: localhost to dst addr: a public IP
-        let new_session = connect(&peer, Some("127.0.0.1:0".parse().unwrap())).await;
+        let bind_to = BindTo {
+            addr,
+            ..Default::default()
+        };
+        let new_session = connect(&peer, Some(bind_to)).await;
         let error = new_session.unwrap_err();
         // XXX: some system will allow the socket to bind and connect without error, only to timeout
         assert!(error.etype() == &ConnectError || error.etype() == &ConnectTimedout)
@@ -371,4 +445,114 @@ mod tests {
         assert_eq!(err.etype(), &ConnectionClosed);
         assert!(!err.retry());
     }
+
+    #[cfg(target_os = "linux")]
+    #[tokio::test(flavor = "multi_thread")]
+    async fn test_bind_to_port_range_on_connect() {
+        fn get_ip_local_port_range() -> (u16, u16) {
+            let path = "/proc/sys/net/ipv4/ip_local_port_range";
+            let file = std::fs::read_to_string(path).unwrap();
+            let mut parts = file.split_whitespace();
+            (
+                parts.next().unwrap().parse().unwrap(),
+                parts.next().unwrap().parse().unwrap(),
+            )
+        }
+
+        // one-off mock server
+        async fn mock_inet_connect_server() {
+            use tokio::net::TcpListener;
+            let listener = TcpListener::bind("127.0.0.1:10020").await.unwrap();
+            if let Ok((mut stream, _addr)) = listener.accept().await {
+                stream.write_all(b"HTTP/1.1 200 OK\r\n\r\n").await.unwrap();
+                // wait a bit so that the client can read
+                tokio::time::sleep(std::time::Duration::from_millis(100)).await;
+            }
+        }
+
+        fn in_port_range(session: Stream, lower: u16, upper: u16) -> bool {
+            let digest = session.get_socket_digest();
+            let local_addr = digest
+                .as_ref()
+                .and_then(|s| s.local_addr())
+                .unwrap()
+                .as_inet()
+                .unwrap();
+
+            // assert range
+            local_addr.port() >= lower && local_addr.port() <= upper
+        }
+
+        tokio::spawn(async {
+            mock_inet_connect_server().await;
+        });
+        // wait for the server to start
+        tokio::time::sleep(std::time::Duration::from_millis(100)).await;
+
+        // need to read /proc/sys/net/ipv4/ip_local_port_range for this test to work
+        // IP_LOCAL_PORT_RANGE clamp only works on ports in /proc/sys/net/ipv4/ip_local_port_range
+        let (low, _) = get_ip_local_port_range();
+        let high = low + 1;
+
+        let peer = HttpPeer::new("127.0.0.1:10020".to_string(), false, "".to_string());
+        let mut bind_to = BindTo {
+            addr: "127.0.0.1:0".parse().ok(),
+            ..Default::default()
+        };
+        bind_to.set_port_range(Some((low, high))).unwrap();
+
+        let session1 = connect(&peer, Some(bind_to.clone())).await.unwrap();
+        assert!(in_port_range(session1, low, high));
+
+        // execute more connect()
+        let session2 = connect(&peer, Some(bind_to.clone())).await.unwrap();
+        assert!(in_port_range(session2, low, high));
+        let session3 = connect(&peer, Some(bind_to.clone())).await.unwrap();
+        assert!(in_port_range(session3, low, high));
+
+        // disabled fallback, should be AddrNotAvailable error
+        let err = connect(&peer, Some(bind_to.clone())).await.unwrap_err();
+        assert_eq!(err.etype(), &InternalError);
+
+        // enable fallback, assert not in port range but successful
+        bind_to.set_fallback(true);
+        let session4 = connect(&peer, Some(bind_to.clone())).await.unwrap();
+        assert!(!in_port_range(session4, low, high));
+
+        // works without bind IP, shift up to use new ports
+        let low = low + 2;
+        let high = low + 1;
+        let mut bind_to = BindTo::default();
+        bind_to.set_port_range(Some((low, high))).unwrap();
+        let session5 = connect(&peer, Some(bind_to.clone())).await.unwrap();
+        assert!(in_port_range(session5, low, high));
+    }
+
+    #[test]
+    fn test_bind_to_port_ranges() {
+        let addr = "127.0.0.1:0".parse().ok();
+        let mut bind_to = BindTo {
+            addr,
+            ..Default::default()
+        };
+
+        // None because the previous value was None
+        bind_to.set_port_range(None).unwrap();
+        assert!(bind_to.port_range.is_none());
+
+        // zeroes are handled
+        bind_to.set_port_range(Some((0, 0))).unwrap();
+        assert_eq!(bind_to.port_range, Some((0, 0)));
+
+        // zeroes because the previous value was Some
+        bind_to.set_port_range(None).unwrap();
+        assert_eq!(bind_to.port_range, Some((0, 0)));
+
+        // low > high is error
+        assert!(bind_to.set_port_range(Some((2000, 1000))).is_err());
+
+        // low < high success
+        bind_to.set_port_range(Some((1000, 2000))).unwrap();
+        assert_eq!(bind_to.port_range, Some((1000, 2000)));
+    }
 }
diff --git a/pingora-core/src/connectors/mod.rs b/pingora-core/src/connectors/mod.rs
index 2d4584c..cbe299f 100644
--- a/pingora-core/src/connectors/mod.rs
+++ b/pingora-core/src/connectors/mod.rs
@@ -24,8 +24,8 @@ use crate::server::configuration::ServerConf;
 use crate::tls::ssl::SslConnector;
 use crate::upstreams::peer::{Peer, ALPN};
 
-use l4::connect as l4_connect;
 pub use l4::Connect as L4Connect;
+use l4::{connect as l4_connect, BindTo};
 use log::{debug, error, warn};
 use offload::OffloadRuntime;
 use parking_lot::RwLock;
@@ -273,7 +273,7 @@ impl TransportConnector {
 // connection timeout if there is one
 async fn do_connect<P: Peer + Send + Sync>(
     peer: &P,
-    bind_to: Option<SocketAddr>,
+    bind_to: Option<BindTo>,
     alpn_override: Option<ALPN>,
     tls_ctx: &SslConnector,
 ) -> Result<Stream> {
@@ -296,7 +296,7 @@ async fn do_connect<P: Peer + Send + Sync>(
 // Perform the actual L4 and tls connection steps with no timeout
 async fn do_connect_inner<P: Peer + Send + Sync>(
     peer: &P,
-    bind_to: Option<SocketAddr>,
+    bind_to: Option<BindTo>,
     alpn_override: Option<ALPN>,
     tls_ctx: &SslConnector,
 ) -> Result<Stream> {
diff --git a/pingora-core/src/protocols/l4/ext.rs b/pingora-core/src/protocols/l4/ext.rs
index 5123bdf..4b65f84 100644
--- a/pingora-core/src/protocols/l4/ext.rs
+++ b/pingora-core/src/protocols/l4/ext.rs
@@ -27,6 +27,8 @@ use std::os::unix::io::{AsRawFd, RawFd};
 use std::time::Duration;
 use tokio::net::{TcpSocket, TcpStream, UnixStream};
 
+use crate::connectors::l4::BindTo;
+
 /// The (copy of) the kernel struct tcp_info returns
 #[repr(C)]
 #[derive(Copy, Clone, Debug)]
@@ -160,9 +162,12 @@ fn cvt_linux_error(t: i32) -> io::Result<i32> {
 
 #[cfg(target_os = "linux")]
 fn ip_bind_addr_no_port(fd: RawFd, val: bool) -> io::Result<()> {
-    const IP_BIND_ADDRESS_NO_PORT: i32 = 24;
-
-    set_opt(fd, libc::IPPROTO_IP, IP_BIND_ADDRESS_NO_PORT, val as c_int)
+    set_opt(
+        fd,
+        libc::IPPROTO_IP,
+        libc::IP_BIND_ADDRESS_NO_PORT,
+        val as c_int,
+    )
 }
 
 #[cfg(not(target_os = "linux"))]
@@ -170,6 +175,26 @@ fn ip_bind_addr_no_port(_fd: RawFd, _val: bool) -> io::Result<()> {
     Ok(())
 }
 
+/// IP_LOCAL_PORT_RANGE is only supported on Linux 6.3 and higher,
+/// ip_local_port_range() is a no-op on unsupported versions.
+/// See the [man page](https://man7.org/linux/man-pages/man7/ip.7.html) for more details.
+#[cfg(target_os = "linux")]
+fn ip_local_port_range(fd: RawFd, low: u16, high: u16) -> io::Result<()> {
+    const IP_LOCAL_PORT_RANGE: i32 = 51;
+    let range: u32 = (low as u32) | ((high as u32) << 16);
+
+    let result = set_opt(fd, libc::IPPROTO_IP, IP_LOCAL_PORT_RANGE, range as c_int);
+    match result {
+        Err(e) if e.raw_os_error() != Some(libc::ENOPROTOOPT) => Err(e),
+        _ => Ok(()), // no error or ENOPROTOOPT
+    }
+}
+
+#[cfg(not(target_os = "linux"))]
+fn ip_local_port_range(_fd: RawFd, _low: u16, _high: u16) -> io::Result<()> {
+    Ok(())
+}
+
 #[cfg(target_os = "linux")]
 fn set_so_keepalive(fd: RawFd, val: bool) -> io::Result<()> {
     set_opt(fd, libc::SOL_SOCKET, libc::SO_KEEPALIVE, val as c_int)
@@ -310,14 +335,42 @@ pub fn get_socket_cookie(_fd: RawFd) -> io::Result<u64> {
     Ok(0) // SO_COOKIE is a Linux concept
 }
 
-/// connect() to the given address while optionally binding to the specific source address.
+/// connect() to the given address while optionally binding to the specific source address and port range.
 ///
 /// The `set_socket` callback can be used to tune the socket before `connect()` is called.
 ///
+/// If a [`BindTo`] is set with a port range and fallback setting enabled this function will retry
+/// on EADDRNOTAVAIL ignoring the port range.
+///
 /// `IP_BIND_ADDRESS_NO_PORT` is used.
-pub(crate) async fn connect_with<F: FnOnce(&TcpSocket) -> Result<()>>(
+/// `IP_LOCAL_PORT_RANGE` is used if a port range is set on [`BindTo`].
+pub(crate) async fn connect_with<F: FnOnce(&TcpSocket) -> Result<()> + Clone>(
     addr: &SocketAddr,
-    bind_to: Option<&SocketAddr>,
+    bind_to: Option<&BindTo>,
+    set_socket: F,
+) -> Result<TcpStream> {
+    if bind_to.as_ref().map_or(false, |b| b.will_fallback()) {
+        // if we see an EADDRNOTAVAIL error clear the port range and try again
+        let connect_result = inner_connect_with(addr, bind_to, set_socket.clone()).await;
+        if let Err(e) = connect_result.as_ref() {
+            if matches!(e.etype(), BindError) {
+                let mut new_bind_to = BindTo::default();
+                new_bind_to.addr = bind_to.as_ref().and_then(|b| b.addr);
+                // reset the port range
+                new_bind_to.set_port_range(None).unwrap();
+                return inner_connect_with(addr, Some(&new_bind_to), set_socket).await;
+            }
+        }
+        connect_result
+    } else {
+        // not retryable
+        inner_connect_with(addr, bind_to, set_socket).await
+    }
+}
+
+async fn inner_connect_with<F: FnOnce(&TcpSocket) -> Result<()>>(
+    addr: &SocketAddr,
+    bind_to: Option<&BindTo>,
     set_socket: F,
 ) -> Result<TcpStream> {
     let socket = if addr.is_ipv4() {
@@ -328,14 +381,23 @@ pub(crate) async fn connect_with<F: FnOnce(&TcpSocket) -> Result<()>>(
     .or_err(SocketError, "failed to create socket")?;
 
     if cfg!(target_os = "linux") {
-        ip_bind_addr_no_port(socket.as_raw_fd(), true)
-            .or_err(SocketError, "failed to set socket opts")?;
-
-        if let Some(baddr) = bind_to {
-            socket
-                .bind(*baddr)
-                .or_err_with(BindError, || format!("failed to bind to socket {}", *baddr))?;
-        };
+        ip_bind_addr_no_port(socket.as_raw_fd(), true).or_err(
+            SocketError,
+            "failed to set socket opts IP_BIND_ADDRESS_NO_PORT",
+        )?;
+
+        if let Some(bind_to) = bind_to {
+            if let Some((low, high)) = bind_to.port_range() {
+                ip_local_port_range(socket.as_raw_fd(), low, high)
+                    .or_err(SocketError, "failed to set socket opts IP_LOCAL_PORT_RANGE")?;
+            }
+
+            if let Some(baddr) = bind_to.addr {
+                socket
+                    .bind(baddr)
+                    .or_err_with(BindError, || format!("failed to bind to socket {}", baddr))?;
+            }
+        }
     }
     // TODO: add support for bind on other platforms
 
@@ -349,8 +411,9 @@ pub(crate) async fn connect_with<F: FnOnce(&TcpSocket) -> Result<()>>(
 
 /// connect() to the given address while optionally binding to the specific source address.
 ///
-/// `IP_BIND_ADDRESS_NO_PORT` is used.
-pub async fn connect(addr: &SocketAddr, bind_to: Option<&SocketAddr>) -> Result<TcpStream> {
+/// `IP_BIND_ADDRESS_NO_PORT` is used
+/// `IP_LOCAL_PORT_RANGE` is used if a port range is set on [`BindTo`].
+pub async fn connect(addr: &SocketAddr, bind_to: Option<&BindTo>) -> Result<TcpStream> {
     connect_with(addr, bind_to, |_| Ok(())).await
 }
 
@@ -365,7 +428,8 @@ fn wrap_os_connect_error(e: std::io::Error, context: String) -> Box<Error> {
     match e.kind() {
         ErrorKind::ConnectionRefused => Error::because(ConnectRefused, context, e),
         ErrorKind::TimedOut => Error::because(ConnectTimedout, context, e),
-        ErrorKind::PermissionDenied | ErrorKind::AddrInUse | ErrorKind::AddrNotAvailable => {
+        ErrorKind::AddrNotAvailable => Error::because(BindError, context, e),
+        ErrorKind::PermissionDenied | ErrorKind::AddrInUse => {
             Error::because(InternalError, context, e)
         }
         _ => match e.raw_os_error() {
diff --git a/pingora-core/src/upstreams/peer.rs b/pingora-core/src/upstreams/peer.rs
index fad8471..832791d 100644
--- a/pingora-core/src/upstreams/peer.rs
+++ b/pingora-core/src/upstreams/peer.rs
@@ -29,7 +29,7 @@ use std::path::{Path, PathBuf};
 use std::sync::Arc;
 use std::time::Duration;
 
-use crate::connectors::L4Connect;
+use crate::connectors::{l4::BindTo, L4Connect};
 use crate::protocols::l4::socket::SocketAddr;
 use crate::protocols::ConnFdReusable;
 use crate::protocols::TcpKeepalive;
@@ -110,8 +110,8 @@ pub trait Peer: Display + Clone {
             None => None,
         }
     }
-    /// Which local source address this connection should be bind to.
-    fn bind_to(&self) -> Option<&InetSocketAddr> {
+    /// Information about the local source address this connection should be bound to.
+    fn bind_to(&self) -> Option<&BindTo> {
         match self.get_peer_options() {
             Some(opt) => opt.bind_to.as_ref(),
             None => None,
@@ -243,7 +243,7 @@ impl Peer for BasicPeer {
         !self.sni.is_empty()
     }
 
-    fn bind_to(&self) -> Option<&InetSocketAddr> {
+    fn bind_to(&self) -> Option<&BindTo> {
         None
     }
 
@@ -294,7 +294,7 @@ impl Scheme {
 /// See [`Peer`] for the meaning of the fields
 #[derive(Clone, Debug)]
 pub struct PeerOptions {
-    pub bind_to: Option<InetSocketAddr>,
+    pub bind_to: Option<BindTo>,
     pub connection_timeout: Option<Duration>,
     pub total_connection_timeout: Option<Duration>,
     pub read_timeout: Option<Duration>,
@@ -365,7 +365,7 @@ impl PeerOptions {
 
 impl Display for PeerOptions {
     fn fmt(&self, f: &mut Formatter<'_>) -> FmtResult {
-        if let Some(b) = self.bind_to {
+        if let Some(b) = self.bind_to.as_ref() {
             write!(f, "bind_to: {:?},", b)?;
         }
         if let Some(t) = self.connection_timeout {