From: Nick Mathewson <nickm@torproject.org>
Date: Mon, 9 Jan 2012 16:49:41 +0000 (-0500)
Subject: Make evconnlistener work around bug in older Linux when getting nmapped
X-Git-Tag: release-2.0.17-stable~23
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=ecfc720a4f7666d468413a3b9b29908bff5ddb82;p=libevent

Make evconnlistener work around bug in older Linux when getting nmapped

Older Linuxes sometimes respond to some nmap probes by having accept()
return a success but with socklen 0.  That can lead to confusing behavior
when you go to process the sockaddr.
---

diff --git a/listener.c b/listener.c
index a440f465..8dcbb0b3 100644
--- a/listener.c
+++ b/listener.c
@@ -390,6 +390,12 @@ listener_read_cb(evutil_socket_t fd, short what, void *p)
 		evutil_socket_t new_fd = accept(fd, (struct sockaddr*)&ss, &socklen);
 		if (new_fd < 0)
 			break;
+		if (socklen == 0) {
+			/* This can happen with some older linux kernels in
+			 * response to nmap. */
+			evutil_closesocket(new_fd);
+			continue;
+		}
 
 		if (!(lev->flags & LEV_OPT_LEAVE_SOCKETS_BLOCKING))
 			evutil_make_socket_nonblocking(new_fd);