From f294a11285f5c79666660d517a3b437718e391dd Mon Sep 17 00:00:00 2001
From: Evan Rittenhouse <erittenhouse@cloudflare.com>
Date: Wed, 24 Apr 2024 08:53:03 -0500
Subject: [PATCH] Add socket creation module

---
 dgram/src/lib.rs    |   1 +
 dgram/src/socket.rs | 133 ++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 134 insertions(+)
 create mode 100644 dgram/src/socket.rs

diff --git a/dgram/src/lib.rs b/dgram/src/lib.rs
index cbd41d5519..88159beb17 100644
--- a/dgram/src/lib.rs
+++ b/dgram/src/lib.rs
@@ -1,2 +1,3 @@
 pub mod async_socket;
+pub mod socket;
 pub mod syscalls;
diff --git a/dgram/src/socket.rs b/dgram/src/socket.rs
new file mode 100644
index 0000000000..9aa9a1e706
--- /dev/null
+++ b/dgram/src/socket.rs
@@ -0,0 +1,133 @@
+use std::io;
+use std::os::fd::AsRawFd;
+use std::os::fd::RawFd;
+
+/// Indicators of settings applied to a socket. These settings aren't "applied"
+/// to a socket. Rather, the same (maximal) settings are always applied to a
+/// socket, and this struct indicates which of those settings were successfully
+/// applied to a socket.
+#[derive(Default)]
+pub struct SocketCapabilities {
+    /// Indicates if the socket has "Generic Segmentation Offload" enabled.
+    has_gso: bool,
+
+    /// Indicates if the socket has "SO_RXQ_OVFL" set.
+    check_udp_drop: bool,
+
+    /// Indicates if the monotonic clock is set for transimssion timestamps.
+    has_txtime: bool,
+
+    /// Indicates if the monotonic clock is set for receiving timestamps.
+    has_rxtime: bool,
+
+    /// Indicates if the socket has "Generic Receive Offload" enabled.
+    has_gro: bool,
+}
+
+impl SocketCapabilities {
+    /// Try applying maximal settings to a socket and returns indicators of
+    /// which settings were successfully applied.
+    #[cfg(unix)]
+    pub fn apply_all_and_get_compatibility<S>(
+        socket: &S, max_send_udp_payload_size: usize,
+    ) -> Self
+    where
+        S: AsRawFd,
+    {
+        let raw_fd = socket.as_raw_fd();
+
+        Self {
+            has_gso: set_udp_segment(raw_fd, max_send_udp_payload_size).is_ok(),
+            check_udp_drop: set_udp_rxq_ovfl(socket).is_ok(),
+            has_txtime: set_tx_time(raw_fd).is_ok(),
+            has_rxtime: set_rx_time(raw_fd).is_ok(),
+            has_gro: set_gro(raw_fd).is_ok(),
+        }
+    }
+}
+
+#[cfg(target_os = "linux")]
+pub fn set_udp_segment(sock: RawFd, segment: usize) -> io::Result<()> {
+    use nix::sys::socket::setsockopt;
+    use nix::sys::socket::sockopt::UdpGsoSegment;
+
+    setsockopt(sock, UdpGsoSegment, &(segment as i32))?;
+
+    Ok(())
+}
+
+#[cfg(target_os = "linux")]
+pub fn set_gro(sock: RawFd) -> io::Result<()> {
+    use nix::sys::socket::sockopt::UdpGroSegment;
+    use nix::sys::socket::SetSockOpt;
+
+    UdpGroSegment.set(sock, &true)?;
+
+    Ok(())
+}
+
+#[cfg(any(target_os = "android", target_os = "ios", target_os = "macos"))]
+pub fn set_gro(_: RawFd) -> io::Result<()> {
+    Err("unsupported").into_io()
+}
+
+#[cfg(any(target_os = "android", target_os = "ios", target_os = "macos"))]
+pub fn set_udp_segment(_: RawFd, _: usize) -> io::Result<()> {
+    Err("unsupported").into_io()
+}
+
+#[cfg(target_os = "linux")]
+fn set_udp_rxq_ovfl<S>(sock: &S) -> io::Result<()>
+where
+    S: AsRawFd,
+{
+    use nix::sys::socket::setsockopt;
+    use nix::sys::socket::sockopt::RxqOvfl;
+
+    setsockopt(sock.as_raw_fd(), RxqOvfl, &1)?;
+
+    Ok(())
+}
+
+#[cfg(any(target_os = "android", target_os = "ios", target_os = "macos"))]
+fn set_udp_rxq_ovfl<S>(_: &S) -> io::Result<()>
+where
+    S: AsRawFd,
+{
+    Err("unsupported").into_io()
+}
+
+#[cfg(target_os = "linux")]
+pub fn set_tx_time(sock: RawFd) -> io::Result<()> {
+    use nix::sys::socket::setsockopt;
+    use nix::sys::socket::sockopt::TxTime;
+
+    let cfg = libc::sock_txtime {
+        clockid: libc::CLOCK_MONOTONIC,
+        flags: 0,
+    };
+
+    setsockopt(sock, TxTime, &cfg)?;
+
+    Ok(())
+}
+
+#[cfg(any(target_os = "android", target_os = "ios", target_os = "macos"))]
+pub fn set_tx_time(_: RawFd) -> io::Result<()> {
+    Err("unsupported").into_io()
+}
+
+#[cfg(target_os = "linux")]
+pub fn set_rx_time(sock: RawFd) -> io::Result<()> {
+    use nix::sys::socket::setsockopt;
+    use nix::sys::socket::sockopt::ReceiveTimestampns;
+
+    setsockopt(sock, ReceiveTimestampns, &true)?;
+
+    Ok(())
+}
+
+#[cfg(target_os = "macos")]
+pub fn set_rx_time(_: RawFd) -> io::Result<()> {
+    Err("unsupported").into_io()
+}