feat: allow setting IPPROTO_TCP as protocol in socket syscall

Author: WhySoBad

src/shims/unix/socket.rs

@@ -316,10 +316,10 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
                 flags
             );
         }
-        if protocol != 0 {
+        if protocol != 0 && protocol != this.eval_libc_i32("IPPROTO_TCP") {
             throw_unsup_format!(
                 "socket: socket protocol {protocol} is unsupported, \
-                only 0 is allowed"
+                only IPPROTO_TCP and 0 are allowed"
             );
         }
 

tests/pass-dep/libc/libc-socket.rs

@@ -16,6 +16,7 @@ const TEST_BYTES: &[u8] = b"these are some test bytes!";
 
 fn main() {
     test_create_close();
+    test_create_close_tcp();
     test_bind_ipv4();
     test_bind_ipv4_reuseaddr();
     test_set_reuseaddr_invalid_len();
@@ -59,6 +60,21 @@ fn test_create_close() {
     unsafe { errno_check(libc::close(sockfd)) };
 }
 
+/// Test creating a socket and then closing it afterwards but we explicitly
+/// specify that the TCP protocol should be used.
+fn test_create_close_tcp() {
+    let sockfd = unsafe {
+        errno_result(libc::socket(libc::AF_INET, libc::SOCK_STREAM, libc::IPPROTO_TCP)).unwrap()
+    };
+
+    let flags = unsafe { errno_result(libc::fcntl(sockfd, libc::F_GETFL, 0)).unwrap() };
+
+    // Ensure that socket is initially blocking.
+    assert_eq!(flags & libc::O_NONBLOCK, 0);
+
+    unsafe { errno_check(libc::close(sockfd)) };
+}
+
 fn test_bind_ipv4() {
     let sockfd =
         unsafe { errno_result(libc::socket(libc::AF_INET, libc::SOCK_STREAM, 0)).unwrap() };