testing: shrink exhaustion test size to avoid timeouts

Tested via:
```
bazel test \
  //test/syscalls:socket_ipv4_udp_unbound_loopback_nogotsan_test_runsc_ptrace
  --runs_per_test=2000
```

PiperOrigin-RevId: 384773477

2 files changed, 15 insertions, 8 deletions

diff --git a/test/syscalls/linux/socket_ipv4_udp_unbound_loopback_nogotsan.cc b/test/syscalls/linux/socket_ipv4_udp_unbound_loopback_nogotsan.cc
index 7ca6d52e4..a2c6d4491 100644
--- a/test/syscalls/linux/socket_ipv4_udp_unbound_loopback_nogotsan.cc
+++ b/test/syscalls/linux/socket_ipv4_udp_unbound_loopback_nogotsan.cc
@@ -31,7 +31,7 @@ using IPv4UDPUnboundSocketNogotsanTest = SimpleSocketTest;
 // We disable S/R because this test creates a large number of sockets.
 TEST_P(IPv4UDPUnboundSocketNogotsanTest, UDPConnectPortExhaustion) {
   auto receiver1 = ASSERT_NO_ERRNO_AND_VALUE(NewSocket());
-  constexpr int kClients = 65536;
+  const int kClients = ASSERT_NO_ERRNO_AND_VALUE(MaybeLimitEphemeralPorts());
   // Bind the first socket to the loopback and take note of the selected port.
   auto addr = V4Loopback();
   ASSERT_THAT(bind(receiver1->get(), AsSockAddr(&addr.addr), addr.addr_len),
@@ -61,7 +61,7 @@ TEST_P(IPv4UDPUnboundSocketNogotsanTest, UDPConnectPortExhaustion) {
 // We disable S/R because this test creates a large number of sockets.
 TEST_P(IPv4UDPUnboundSocketNogotsanTest, UDPBindPortExhaustion) {
   auto receiver1 = ASSERT_NO_ERRNO_AND_VALUE(NewSocket());
-  constexpr int kClients = 65536;
+  const int kClients = ASSERT_NO_ERRNO_AND_VALUE(MaybeLimitEphemeralPorts());
   auto addr = V4Loopback();
   // Disable cooperative S/R as we are making too many syscalls.
   DisableSave ds;
diff --git a/test/syscalls/linux/socket_test_util.cc b/test/syscalls/linux/socket_test_util.cc
index 1afb1ab50..c1cded834 100644
--- a/test/syscalls/linux/socket_test_util.cc
+++ b/test/syscalls/linux/socket_test_util.cc
@@ -1093,14 +1093,21 @@ PosixErrorOr<int> MaybeLimitEphemeralPorts() {
   if (!access(kRangeFile, W_OK)) {
     ASSIGN_OR_RETURN_ERRNO(FileDescriptor fd,
                            Open(kRangeFile, O_WRONLY | O_TRUNC, 0));
-    max = min + 50;
-    const std::string small_range = absl::StrFormat("%d %d", min, max);
+    int newMax = min + 50;
+    const std::string small_range = absl::StrFormat("%d %d", min, newMax);
     int n = write(fd.get(), small_range.c_str(), small_range.size());
     if (n < 0) {
-      return PosixError(
-          errno,
-          absl::StrFormat("write(%d [%s], \"%s\", %d)", fd.get(), kRangeFile,
-                          small_range.c_str(), small_range.size()));
+      // Hostinet doesn't allow modifying the host port range. And if we're root
+      // (as we are in some tests), access and open will succeed even if the
+      // file mode is readonly.
+      if (errno != EACCES) {
+        return PosixError(
+            errno,
+            absl::StrFormat("write(%d [%s], \"%s\", %d)", fd.get(), kRangeFile,
+                            small_range.c_str(), small_range.size()));
+      }
+    } else {
+      max = newMax;
     }
   }
   return max - min;