Fix: set_ipv6_multicast_hops on unix

crates/wtfnet-probe/Cargo.toml

@@ -11,3 +11,4 @@ thiserror = "2"
 tokio = { version = "1", features = ["net", "time"] }
 surge-ping = "0.8"
 wtfnet-geoip = { path = "../wtfnet-geoip" }
+libc = "0.2"

crates/wtfnet-probe/src/lib.rs

@@ -9,9 +9,12 @@ use pnet::transport::{
     TransportChannelType, TransportProtocol, icmp_packet_iter, icmpv6_packet_iter,
     transport_channel,
 };
+#[cfg(unix)]
+use std::os::unix::io::AsRawFd;
 use serde::{Deserialize, Serialize};
 use socket2::{Domain, Protocol, Socket, Type};
 use std::net::{IpAddr, SocketAddr};
+use std::mem::size_of_val;
 use std::time::{Duration, Instant};
 use thiserror::Error;
 use tokio::net::{TcpStream, lookup_host};
@@ -473,9 +476,7 @@ fn udp_trace_hop_v6(
 
     let socket =
         std::net::UdpSocket::bind("[::]:0").map_err(|err| ProbeError::Io(err.to_string()))?;
-    socket
-        .set_unicast_hops_v6(u32::from(ttl))
-        .map_err(|err| ProbeError::Io(err.to_string()))?;
+    set_ipv6_unicast_hops(&socket, ttl)?;
     let _ = socket.send_to(&[0u8; 4], addr);
 
     let mut iter = icmpv6_packet_iter(&mut rx);
@@ -491,6 +492,28 @@ fn udp_trace_hop_v6(
     }
 }
 
+#[cfg(unix)]
+fn set_ipv6_unicast_hops(socket: &std::net::UdpSocket, ttl: u8) -> Result<(), ProbeError> {
+    let fd = socket.as_raw_fd();
+    let hops: libc::c_int = ttl.into();
+    let result = unsafe {
+        libc::setsockopt(
+            fd,
+            libc::IPPROTO_IPV6,
+            libc::IPV6_UNICAST_HOPS,
+            &hops as *const _ as *const libc::c_void,
+            size_of_val(&hops) as libc::socklen_t,
+        )
+    };
+    if result == 0 {
+        Ok(())
+    } else {
+        Err(ProbeError::Io(
+            std::io::Error::last_os_error().to_string(),
+        ))
+    }
+}
+
 #[cfg(unix)]
 fn interpret_icmp_v4(packet: &IcmpPacket) -> Option<bool> {
     let icmp_type = packet.get_icmp_type();