Make multicast-group helpers and vsock fallback portable to QNX (#20)

* Make multicast-group helpers and vsock fallback portable to QNX

Two small portability fixes so this builds on QNX (and stays building
on macOS / BSDs):

  * UDPSocket::JoinMulticastGroup / LeaveMulticastGroup used the
    Linux-only struct ip_mreqn (with imr_ifindex).  Switch to the
    POSIX-portable struct ip_mreq.  Behaviour is unchanged on Linux:
    the previous code passed imr_ifindex = 0, which is equivalent to
    INADDR_ANY in ip_mreq.imr_interface.

  * The fallback definition of struct sockaddr_vm in sockets.h had a
    typo `_APPLE__` (single leading underscore).  This is harmless on
    Apple, where <sys/vsock.h> is used instead, but on a system that
    actually hits the fallback (e.g. QNX) a true `__APPLE__` macro
    would never have inserted svm_len.  Fix the spelling.

Made-with: Cursor

* Fix bazel test //...

Author: dallison

.bazelignore

@@ -1 +1,3 @@
 bazel-toolbelt
+_deps
+build

MODULE.bazel.lock

@@ -82,7 +82,7 @@ cc_test(
 )
 cc_test(
     name = "pipe_test",
-    size = "small",
+    size = "medium",
     srcs = ["pipe_test.cc"],
     deps = [
         ":toolbelt",

toolbelt/BUILD.bazel

@@ -799,9 +799,13 @@ absl::Status UDPSocket::Bind(const InetAddress &addr) {
 }
 
 absl::Status UDPSocket::JoinMulticastGroup(const InetAddress &addr) {
-  ip_mreqn membership_request{.imr_multiaddr = addr.GetAddress().sin_addr,
-                              .imr_address = {INADDR_ANY},
-                              .imr_ifindex = 0};
+  // Use POSIX-portable ip_mreq instead of Linux-specific ip_mreqn so this
+  // builds on macOS, BSDs and QNX as well.  We always join via the default
+  // interface (INADDR_ANY); callers needing per-interface control should
+  // extend this API.
+  struct ip_mreq membership_request = {};
+  membership_request.imr_multiaddr = addr.GetAddress().sin_addr;
+  membership_request.imr_interface.s_addr = htonl(INADDR_ANY);
   int setsockopt_ret =
       ::setsockopt(fd_.Fd(), IPPROTO_IP, IP_ADD_MEMBERSHIP, &membership_request,
                    sizeof(membership_request));
@@ -815,9 +819,9 @@ absl::Status UDPSocket::JoinMulticastGroup(const InetAddress &addr) {
 }
 
 absl::Status UDPSocket::LeaveMulticastGroup(const InetAddress &addr) {
-  ip_mreqn membership_request{.imr_multiaddr = addr.GetAddress().sin_addr,
-                              .imr_address = {INADDR_ANY},
-                              .imr_ifindex = 0};
+  struct ip_mreq membership_request = {};
+  membership_request.imr_multiaddr = addr.GetAddress().sin_addr;
+  membership_request.imr_interface.s_addr = htonl(INADDR_ANY);
   int setsockopt_ret =
       ::setsockopt(fd_.Fd(), IPPROTO_IP, IP_DROP_MEMBERSHIP,
                    &membership_request, sizeof(membership_request));

toolbelt/sockets.cc

@@ -37,7 +37,7 @@
 // Older systems may not have the header file.
 #if !HAS_VM_SOCKETS
 struct sockaddr_vm {
-#if defined(_APPLE__)
+#if defined(__APPLE__)
   uint8_t svm_len;      /* total length of sockaddr */
 #endif
   sa_family_t svm_family; /* AF_VSOCK */