syscalls: minor refactor, adding coverage (envoyproxy#36075)

minor refactor no longer fast-failing if the system can't create
sockets.

Risk Level: low
Testing: added tests, manually tested fd failure
Docs Changes: n/a
Release Notes: n/a

---------

Signed-off-by: Fredy Wijaya <fredyw@google.com>
Signed-off-by: Alyssa Wilk <alyssar@chromium.org>
Co-authored-by: Fredy Wijaya <fredyw@google.com>

source/common/api/posix/os_sys_calls_impl.cc

@@ -109,9 +109,6 @@ bool OsSysCallsImpl::supportsUdpGro() const {
 #else
   static const bool is_supported = [] {
     int fd = ::socket(AF_INET, SOCK_DGRAM | SOCK_NONBLOCK, IPPROTO_UDP);
-    if (fd < 0) {
-      return false;
-    }
     int val = 1;
     bool result = (0 == ::setsockopt(fd, IPPROTO_UDP, UDP_GRO, &val, sizeof(val)));
     ::close(fd);
@@ -127,9 +124,6 @@ bool OsSysCallsImpl::supportsUdpGso() const {
 #else
   static const bool is_supported = [] {
     int fd = ::socket(AF_INET, SOCK_DGRAM | SOCK_NONBLOCK, IPPROTO_UDP);
-    if (fd < 0) {
-      return false;
-    }
     int optval;
     socklen_t optlen = sizeof(optval);
     bool result = (0 <= ::getsockopt(fd, IPPROTO_UDP, UDP_SEGMENT, &optval, &optlen));
@@ -160,9 +154,6 @@ bool OsSysCallsImpl::supportsIpTransparent(Network::Address::IpVersion ip_versio
   static constexpr auto transparent_supported = [](int family) {
     auto opt_tp = family == AF_INET ? ENVOY_SOCKET_IP_TRANSPARENT : ENVOY_SOCKET_IPV6_TRANSPARENT;
     int fd = ::socket(family, SOCK_DGRAM | SOCK_NONBLOCK, IPPROTO_UDP);
-    if (fd < 0) {
-      return false;
-    }
     int val = 1;
     bool result = (0 == ::setsockopt(fd, opt_tp.level(), opt_tp.option(), &val, sizeof(val)));
     ::close(fd);
@@ -348,9 +339,9 @@ SysCallBoolResult OsSysCallsImpl::socketTcpInfo([[maybe_unused]] os_fd_t sockfd,
     tcp_info->tcpi_snd_cwnd = unix_tcp_info.tcpi_snd_cwnd * mss;
   }
   return {!SOCKET_FAILURE(result), !SOCKET_FAILURE(result) ? 0 : errno};
-#endif
-
+#else
   return {false, EOPNOTSUPP};
+#endif
 }
 
 bool OsSysCallsImpl::supportsGetifaddrs() const { return true; }

test/common/api/os_sys_calls_test.cc

@@ -68,4 +68,19 @@ TEST(OsSyscallsTest, OpenPwritePreadFstatCloseStatUnlink) {
   TestEnvironment::removePath(path);
 }
 
+TEST(OsSyscallsTest, SupportsIpTransparent) {
+  bool supported = Api::OsSysCallsSingleton::get().supportsIpTransparent(
+      TestEnvironment::getIpVersionsForTest()[0]);
+  EXPECT_FALSE(supported);
+}
+
+TEST(OsSyscallsTest, SupportsMptcp) {
+  bool supported = Api::OsSysCallsSingleton::get().supportsMptcp();
+  EXPECT_TRUE(supported);
+}
+
+TEST(OsSyscallsTest, IoCtlInvalidFd) {
+  EXPECT_NE(0, Api::OsSysCallsSingleton::get().ioctl(0, 0, nullptr, 0, nullptr, 0, nullptr).errno_);
+}
+
 } // namespace Envoy

test/per_file_coverage.sh

@@ -4,8 +4,6 @@
 # for existing directories with low coverage.
 declare -a KNOWN_LOW_COVERAGE=(
 "source/common:96.2"
-"source/common/api:84.5" # flaky due to posix: be careful adjusting
-"source/common/api/posix:83.8" # flaky (accept failover non-deterministic): be careful adjusting
 "source/common/common/posix:96.2" # flaky due to posix: be careful adjusting
 "source/common/config:96.1"
 "source/common/crypto:95.5"