Merge pull request #533 from ohwgiles/master

RPC: Support abstract unix socket addresses on Linux

c++/src/kj/async-io-test.c++

@@ -28,6 +28,8 @@
 #include "windows-sanity.h"
 #else
 #include <netdb.h>
+#include <unistd.h>
+#include <fcntl.h>
 #endif
 
 namespace kj {
@@ -102,6 +104,7 @@ TEST(AsyncIo, AddressParsing) {
 
 #if !_WIN32
   EXPECT_EQ("unix:foo/bar/baz", tryParse(w, network, "unix:foo/bar/baz"));
+  EXPECT_EQ("unix-abstract:foo/bar/baz", tryParse(w, network, "unix-abstract:foo/bar/baz"));
 #endif
 
   // We can parse services by name...
@@ -387,5 +390,27 @@ TEST(AsyncIo, Udp) {
 
 #endif  // !_WIN32
 
+#ifdef __linux__  // Abstract unix sockets are only supported on Linux
+
+TEST(AsyncIo, AbstractUnixSocket) {
+  auto ioContext = setupAsyncIo();
+  auto& network = ioContext.provider->getNetwork();
+
+  Own<NetworkAddress> addr = network.parseAddress("unix-abstract:foo").wait(ioContext.waitScope);
+
+  Own<ConnectionReceiver> listener = addr->listen();
+  // chdir proves no filesystem dependence. Test fails for regular unix socket
+  // but passes for abstract unix socket.
+  int originalDirFd;
+  KJ_SYSCALL(originalDirFd = open(".", O_RDONLY | O_DIRECTORY | O_CLOEXEC));
+  KJ_DEFER(close(originalDirFd));
+  KJ_SYSCALL(chdir("/tmp"));
+  KJ_DEFER(KJ_SYSCALL(fchdir(originalDirFd)));
+
+  addr->connect().attach(kj::mv(listener)).wait(ioContext.waitScope);
+}
+
+#endif  // __linux__
+
 }  // namespace
 }  // namespace kj

c++/src/kj/async-io-unix.c++

@@ -449,7 +449,11 @@ public:
         return str('[', buffer, "]:", ntohs(addr.inet6.sin6_port));
       }
       case AF_UNIX: {
-        return str("unix:", addr.unixDomain.sun_path);
+        if (addr.unixDomain.sun_path[0] == '\0') {
+          return str("unix-abstract:", addr.unixDomain.sun_path + 1);
+        } else {
+          return str("unix:", addr.unixDomain.sun_path);
+        }
       }
       default:
         return str("(unknown address family ", addr.generic.sa_family, ")");
@@ -470,6 +474,9 @@ public:
       StringPtr path = str.slice(strlen("unix:"));
       KJ_REQUIRE(path.size() < sizeof(addr.unixDomain.sun_path),
                  "Unix domain socket address is too long.", str);
+      KJ_REQUIRE(path.size() == strlen(path.cStr()),
+                 "Unix domain socket address contains NULL. Use"
+                 " 'unix-abstract:' for the abstract namespace.");
       result.addr.unixDomain.sun_family = AF_UNIX;
       strcpy(result.addr.unixDomain.sun_path, path.cStr());
       result.addrlen = offsetof(struct sockaddr_un, sun_path) + path.size() + 1;
@@ -478,6 +485,21 @@ public:
       return array.finish();
     }
 
+    if (str.startsWith("unix-abstract:")) {
+      StringPtr path = str.slice(strlen("unix-abstract:"));
+      KJ_REQUIRE(path.size() + 1 < sizeof(addr.unixDomain.sun_path),
+                 "Unix domain socket address is too long.", str);
+      result.addr.unixDomain.sun_family = AF_UNIX;
+      result.addr.unixDomain.sun_path[0] = '\0';
+      // although not strictly required by Linux, also copy the trailing
+      // NULL terminator so that we can safely read it back in toString
+      memcpy(result.addr.unixDomain.sun_path + 1, path.cStr(), path.size() + 1);
+      result.addrlen = offsetof(struct sockaddr_un, sun_path) + path.size() + 1;
+      auto array = kj::heapArrayBuilder<SocketAddress>(1);
+      array.add(result);
+      return array.finish();
+    }
+
     // Try to separate the address and port.
     ArrayPtr<const char> addrPart;
     Maybe<StringPtr> portPart;

doc/cxxrpc.md

@@ -390,7 +390,8 @@ int main(int argc, const char* argv[]) {
 {% endhighlight %}
 
 Note that for the connect address, Cap'n Proto supports DNS host names as well as IPv4 and IPv6
-addresses.  Additionally, a Unix domain socket can be specified as `unix:` followed by a path name.
+addresses.  Additionally, a Unix domain socket can be specified as `unix:` followed by a path name,
+and an abstract Unix domain socket can be specified as `unix-abstract:` followed by an identifier.
 
 For a more complete example, see the
 [calculator client sample](https://github.com/sandstorm-io/capnproto/tree/master/c++/samples/calculator-client.c++).
@@ -429,7 +430,8 @@ int main(int argc, const char* argv[]) {
 Note that for the bind address, Cap'n Proto supports DNS host names as well as IPv4 and IPv6
 addresses.  The special address `*` can be used to bind to the same port on all local IPv4 and
 IPv6 interfaces.  Additionally, a Unix domain socket can be specified as `unix:` followed by a
-path name.
+path name, and an abstract Unix domain socket can be specified as `unix-abstract:` followed by
+an identifier.
 
 For a more complete example, see the
 [calculator server sample](https://github.com/sandstorm-io/capnproto/tree/master/c++/samples/calculator-server.c++).