adb: detect sockets in CLOSE_WAIT state to prevent socket leak on linux.

It is possible that the adb server on host has many sockets in
CLOSE_WAIT state. To prevent socket leak, always enable POLLRDHUP
in fdevent.cpp to detect sockets in CLOSE_WAIT state.

Update LocalSocketTest unit tests:
Change half_close_with_packet to read_from_closing_socket, as reading
from a SHUT_WR socket is not needed in adb.
Change close_with_no_events_installed to close_socket_in_CLOSE_WAIT_state,
as the latter is more close to the real situation in use.

Bug: 23314034

Change-Id: Ice4f4036624e5584eab6ba5848e7f169c92f037f

1 files changed, 11 insertions, 0 deletions

diff --git a/adb/fdevent.cpp b/adb/fdevent.cpp
index 2de9386fd..2ffd908d4 100644
--- a/adb/fdevent.cpp
+++ b/adb/fdevent.cpp
@@ -58,6 +58,12 @@ struct PollNode {
   PollNode(fdevent* fde) : fde(fde) {
       memset(&pollfd, 0, sizeof(pollfd));
       pollfd.fd = fde->fd;
+
+#if defined(__linux__)
+      // Always enable POLLRDHUP, so the host server can take action when some clients disconnect.
+      // Then we can avoid leaving many sockets in CLOSE_WAIT state. See http://b/23314034.
+      pollfd.events = POLLRDHUP;
+#endif
   }
 };
 
@@ -234,6 +240,11 @@ static void fdevent_process() {
             // be detected at that point.
             events |= FDE_READ | FDE_ERROR;
         }
+#if defined(__linux__)
+        if (pollfd.revents & POLLRDHUP) {
+            events |= FDE_READ | FDE_ERROR;
+        }
+#endif
         if (events != 0) {
             auto it = g_poll_node_map.find(pollfd.fd);
             CHECK(it != g_poll_node_map.end());