[PortManager] Prefer ss over netstat on Linux (#91)

ss is a modern alternative to netstat. The flags we use and the way we
parse the output are compatible with netstat. Since netstat is no
longer installed on some Linux distributions, prefer ss, but fall back
to netstat if "which ss" fails.

Also tweaks some logging.

Fixes #65

cdc_rsync/cdc_rsync_client.cc

@@ -146,6 +146,9 @@ absl::Status CdcRsyncClient::Run() {
     // Check whether we guessed the arch type wrong and try again.
     // Note that in case of a local sync, or if the server actively reported
     // that it's out-dated, there's no need to detect the arch.
+    LOG_DEBUG(
+        "Failed to start server, retrying after detecting remote arch: %s",
+        status.ToString());
     const ArchType old_type = server_arch.GetType();
     ASSIGN_OR_RETURN(server_arch,
                      ServerArch::DetectFromRemoteDevice(remote_util_.get()));
@@ -219,6 +222,9 @@ absl::StatusOr<int> CdcRsyncClient::FindAvailablePort(ServerArch* server_arch) {
   // the arch was wrong. Properly detect it and try again if it changed.
   if (!port.ok() && server_arch->IsGuess()) {
     const ArchType old_type = server_arch->GetType();
+    LOG_DEBUG(
+        "Failed to reserve port, retrying after detecting remote arch: %s",
+        port.status().ToString());
     ASSIGN_OR_RETURN(*server_arch,
                      ServerArch::DetectFromRemoteDevice(remote_util_.get()));
     assert(!server_arch->IsGuess());

cdc_rsync/main.cc

@@ -68,8 +68,8 @@ ReturnCode TagToMessage(cdc_ft::Tag tag,
 
     case cdc_ft::Tag::kDeployServer:
       *msg =
-          "Failed to deploy the instance components for unknown reasons. "
+          "Failed to deploy or run the instance components for unknown "
-          "Please report this issue.";
+          "reasons. Please report this issue.";
       return ReturnCode::kDeployFailed;
 
     case cdc_ft::Tag::kConnectionTimeout:

cdc_rsync/zstd_stream.cc

@@ -146,7 +146,7 @@ void ZstdStream::ThreadCompressorMain() {
     const ZSTD_EndDirective mode = last_chunk_ ? ZSTD_e_end
                                    : flush     ? ZSTD_e_flush
                                                : ZSTD_e_continue;
-    LOG_DEBUG("Compressing %u bytes (mode=%s)", in_buffer_.size(),
+    LOG_VERBOSE("Compressing %u bytes (mode=%s)", in_buffer_.size(),
                 mode == ZSTD_e_end     ? "end"
                 : mode == ZSTD_e_flush ? "flush"
                                        : "continue");

common/port_manager_test.cc

@@ -35,12 +35,17 @@ constexpr int kNumPorts = kLastPort - kFirstPort + 1;
 constexpr int kTimeoutSec = 1;
 
 constexpr char kWindowsNetstat[] = "netstat -a -n -p tcp";
-constexpr char kLinuxNetstat[] = "netstat --numeric --listening --tcp";
+constexpr char kLinuxNetstatOrSS[] =
+    "which ss2 && ss --numeric --listening --tcp || netstat --numeric "
+    "--listening --tcp";
 
 constexpr char kWindowsNetstatOutFmt[] =
     "TCP    127.0.0.1:50000        127.0.0.1:%i        ESTABLISHED";
 constexpr char kLinuxNetstatOutFmt[] =
     "tcp        0      0 0.0.0.0:%i           0.0.0.0:*               LISTEN";
+constexpr char kLinuxSSOutFmt[] =
+    "LISTEN              0                    128                              "
+    "             0.0.0.0:%i                                     0.0.0.0:*  ";
 
 class PortManagerTest : public ::testing::Test {
  public:
@@ -67,7 +72,7 @@ class PortManagerTest : public ::testing::Test {
 
 TEST_F(PortManagerTest, ReservePortSuccess) {
   process_factory_.SetProcessOutput(kWindowsNetstat, "", "", 0);
-  process_factory_.SetProcessOutput(kLinuxNetstat, "", "", 0);
+  process_factory_.SetProcessOutput(kLinuxNetstatOrSS, "", "", 0);
 
   absl::StatusOr<int> port =
       port_manager_.ReservePort(kTimeoutSec, ArchType::kLinux_x86_64);
@@ -81,7 +86,7 @@ TEST_F(PortManagerTest, ReservePortAllLocalPortsTaken) {
     local_netstat_out += absl::StrFormat(kWindowsNetstatOutFmt, port);
   }
   process_factory_.SetProcessOutput(kWindowsNetstat, local_netstat_out, "", 0);
-  process_factory_.SetProcessOutput(kLinuxNetstat, "", "", 0);
+  process_factory_.SetProcessOutput(kLinuxNetstatOrSS, "", "", 0);
 
   absl::StatusOr<int> port =
       port_manager_.ReservePort(kTimeoutSec, ArchType::kLinux_x86_64);
@@ -96,7 +101,8 @@ TEST_F(PortManagerTest, ReservePortAllRemotePortsTaken) {
     remote_netstat_out += absl::StrFormat(kLinuxNetstatOutFmt, port);
   }
   process_factory_.SetProcessOutput(kWindowsNetstat, "", "", 0);
-  process_factory_.SetProcessOutput(kLinuxNetstat, remote_netstat_out, "", 0);
+  process_factory_.SetProcessOutput(kLinuxNetstatOrSS, remote_netstat_out, "",
+                                    0);
 
   absl::StatusOr<int> port =
       port_manager_.ReservePort(kTimeoutSec, ArchType::kLinux_x86_64);
@@ -107,7 +113,7 @@ TEST_F(PortManagerTest, ReservePortAllRemotePortsTaken) {
 
 TEST_F(PortManagerTest, ReservePortLocalNetstatFails) {
   process_factory_.SetProcessOutput(kWindowsNetstat, "", "", 1);
-  process_factory_.SetProcessOutput(kLinuxNetstat, "", "", 0);
+  process_factory_.SetProcessOutput(kLinuxNetstatOrSS, "", "", 0);
 
   absl::StatusOr<int> port =
       port_manager_.ReservePort(kTimeoutSec, ArchType::kLinux_x86_64);
@@ -119,7 +125,7 @@ TEST_F(PortManagerTest, ReservePortLocalNetstatFails) {
 
 TEST_F(PortManagerTest, ReservePortRemoteNetstatFails) {
   process_factory_.SetProcessOutput(kWindowsNetstat, "", "", 0);
-  process_factory_.SetProcessOutput(kLinuxNetstat, "", "", 1);
+  process_factory_.SetProcessOutput(kLinuxNetstatOrSS, "", "", 1);
 
   absl::StatusOr<int> port =
       port_manager_.ReservePort(kTimeoutSec, ArchType::kLinux_x86_64);
@@ -130,7 +136,7 @@ TEST_F(PortManagerTest, ReservePortRemoteNetstatFails) {
 
 TEST_F(PortManagerTest, ReservePortRemoteNetstatTimesOut) {
   process_factory_.SetProcessOutput(kWindowsNetstat, "", "", 0);
-  process_factory_.SetProcessNeverExits(kLinuxNetstat);
+  process_factory_.SetProcessNeverExits(kLinuxNetstatOrSS);
   steady_clock_.AutoAdvance(kTimeoutSec * 2 * 1000);
 
   absl::StatusOr<int> port =
@@ -143,7 +149,7 @@ TEST_F(PortManagerTest, ReservePortRemoteNetstatTimesOut) {
 
 TEST_F(PortManagerTest, ReservePortMultipleInstances) {
   process_factory_.SetProcessOutput(kWindowsNetstat, "", "", 0);
-  process_factory_.SetProcessOutput(kLinuxNetstat, "", "", 0);
+  process_factory_.SetProcessOutput(kLinuxNetstatOrSS, "", "", 0);
 
   PortManager port_manager2(kGuid, kFirstPort, kLastPort, &process_factory_,
                             &remote_util_);
@@ -163,7 +169,7 @@ TEST_F(PortManagerTest, ReservePortMultipleInstances) {
 
 TEST_F(PortManagerTest, ReservePortReusesPortsInLRUOrder) {
   process_factory_.SetProcessOutput(kWindowsNetstat, "", "", 0);
-  process_factory_.SetProcessOutput(kLinuxNetstat, "", "", 0);
+  process_factory_.SetProcessOutput(kLinuxNetstatOrSS, "", "", 0);
 
   for (int n = 0; n < kNumPorts * 2; ++n) {
     EXPECT_EQ(*port_manager_.ReservePort(kTimeoutSec, ArchType::kLinux_x86_64),
@@ -174,7 +180,7 @@ TEST_F(PortManagerTest, ReservePortReusesPortsInLRUOrder) {
 
 TEST_F(PortManagerTest, ReleasePort) {
   process_factory_.SetProcessOutput(kWindowsNetstat, "", "", 0);
-  process_factory_.SetProcessOutput(kLinuxNetstat, "", "", 0);
+  process_factory_.SetProcessOutput(kLinuxNetstatOrSS, "", "", 0);
 
   absl::StatusOr<int> port =
       port_manager_.ReservePort(kTimeoutSec, ArchType::kLinux_x86_64);
@@ -186,7 +192,7 @@ TEST_F(PortManagerTest, ReleasePort) {
 
 TEST_F(PortManagerTest, ReleasePortOnDestruction) {
   process_factory_.SetProcessOutput(kWindowsNetstat, "", "", 0);
-  process_factory_.SetProcessOutput(kLinuxNetstat, "", "", 0);
+  process_factory_.SetProcessOutput(kLinuxNetstatOrSS, "", "", 0);
 
   auto port_manager2 = std::make_unique<PortManager>(
       kGuid, kFirstPort, kLastPort, &process_factory_, &remote_util_);
@@ -219,7 +225,8 @@ TEST_F(PortManagerTest, FindAvailableLocalPortsSuccessLinux) {
   // First port is in use.
   std::string local_netstat_out =
       absl::StrFormat(kLinuxNetstatOutFmt, kFirstPort);
-  process_factory_.SetProcessOutput(kLinuxNetstat, local_netstat_out, "", 0);
+  process_factory_.SetProcessOutput(kLinuxNetstatOrSS, local_netstat_out, "",
+                                    0);
 
   absl::StatusOr<std::unordered_set<int>> ports =
       PortManager::FindAvailableLocalPorts(
@@ -251,7 +258,25 @@ TEST_F(PortManagerTest, FindAvailableRemotePortsSuccessLinux) {
   // First port is in use.
   std::string remote_netstat_out =
       absl::StrFormat(kLinuxNetstatOutFmt, kFirstPort);
-  process_factory_.SetProcessOutput(kLinuxNetstat, remote_netstat_out, "", 0);
+  process_factory_.SetProcessOutput(kLinuxNetstatOrSS, remote_netstat_out, "",
+                                    0);
+
+  absl::StatusOr<std::unordered_set<int>> ports =
+      PortManager::FindAvailableRemotePorts(
+          kFirstPort, kLastPort, ArchType::kLinux_x86_64, &process_factory_,
+          &remote_util_, kTimeoutSec);
+  ASSERT_OK(ports);
+  EXPECT_EQ(ports->size(), kNumPorts - 1);
+  for (int port = kFirstPort + 1; port <= kLastPort; ++port) {
+    EXPECT_TRUE(ports->find(port) != ports->end());
+  }
+}
+
+TEST_F(PortManagerTest, FindAvailableRemotePortsSuccessLinuxSS) {
+  // First port is in use, but reporting is done by SS, not netsta.
+  std::string remote_netstat_out = absl::StrFormat(kLinuxSSOutFmt, kFirstPort);
+  process_factory_.SetProcessOutput(kLinuxNetstatOrSS, remote_netstat_out, "",
+                                    0);
 
   absl::StatusOr<std::unordered_set<int>> ports =
       PortManager::FindAvailableRemotePorts(
@@ -287,7 +312,8 @@ TEST_F(PortManagerTest, FindAvailableRemotePortsFailsNoPorts) {
   for (int port = kFirstPort; port <= kLastPort; ++port) {
     remote_netstat_out += absl::StrFormat(kLinuxNetstatOutFmt, port);
   }
-  process_factory_.SetProcessOutput(kLinuxNetstat, remote_netstat_out, "", 0);
+  process_factory_.SetProcessOutput(kLinuxNetstatOrSS, remote_netstat_out, "",
+                                    0);
 
   absl::StatusOr<std::unordered_set<int>> ports =
       PortManager::FindAvailableRemotePorts(

common/port_manager_win.cc

@@ -43,10 +43,12 @@ const char* GetNetstatCommand(ArchType arch_type) {
   }
 
   if (IsLinuxArchType(arch_type)) {
+    // Prefer ss over netstat. The flags out output are compatible.
     // --numeric to get numerical addresses.
     // --listening to get only listening sockets.
     // --tcp to get only TCP connections.
-    return "netstat --numeric --listening --tcp";
+    return "which ss2 && ss --numeric --listening --tcp || netstat "
+           "--numeric --listening --tcp";
   }
 
   assert(!kErrorArchTypeUnhandled);