1 files changed, 25 insertions, 0 deletions

diff --git a/src/rpc.cpp b/src/rpc.cpp
index 4ff09b9..a4b53ca 100644
--- a/src/rpc.cpp
+++ b/src/rpc.cpp
@@ -4697,6 +4697,31 @@ static void PoolEventLoop()
                     sock_close(fd);
                     continue;
                 }
+                // #26: select() + FD_SET goes undefined once we exceed what an
+                // fd_set can carry, and MAX_POOL_MINERS (1000) alone does not
+                // prevent it -- a Miner is only removed on clean disconnect, so
+                // half-open zombies accumulate and the OS can hand out fds past
+                // the limit long before the count reaches 1000. Refuse rather
+                // than corrupt the fd_set. Which limit applies is platform
+                // specific: POSIX bounds the descriptor value, Windows the
+                // number of SOCKET handles an fd_set can hold.
+#ifndef _WIN32
+                if ((int)fd >= (int)FD_SETSIZE) {
+                    LogPrint("worker", "[pool] refusing miner fd=%d -- at/over"
+                             " FD_SETSIZE=%d, select() would be undefined (#26)\n",
+                             (int)fd, (int)FD_SETSIZE);
+                    sock_close(fd);
+                    continue;
+                }
+#else
+                if (gMiners.size() >= (size_t)FD_SETSIZE) {
+                    LogPrint("worker", "[pool] refusing miner -- %zu sockets held,"
+                             " an fd_set carries at most FD_SETSIZE=%d (#26)\n",
+                             gMiners.size(), (int)FD_SETSIZE);
+                    sock_close(fd);
+                    continue;
+                }
+#endif
                 gMiners.push_back(new Miner(fd));
                 LogPrint("worker", "[pool] miner fd=%d entered event loop"
                          " -- awaiting subscribe/authorize\n", (int)fd);