Merge pull request #108 from shivrai/feat/listen-incoming-rst

Test for behavior when sending a packet with RST bit set but no SYN bit set

gtests/net/packetdrill/tests/bsd/tcp/listen/listen-incoming-rst.pkt

+// Test behavior when a listener gets an incoming packet 
+// from a new sender on a non-established session that has
+// the RST bit set but not the SYN bit set.
+// Listener should send a RESET.
+// Checking if we can establish a connection with the 
+// system after a connection reset.
+
+0.000 socket(..., SOCK_STREAM, IPPROTO_TCP) = 3
+0.000 setsockopt(3, SOL_SOCKET, SO_REUSEADDR, [1], 4) = 0
+0.000 bind(3, ..., ...) = 0
+0.000 listen(3, 1) = 0
+
+0.100 < R 0:0(0) win 65535 <mss 1460,sackOK,nop,nop,nop,wscale 7>
+
+// The TCP stack should not respond to incoming RSTs, or else
+// we could get infinite RST ping-pong storms.
+
+// Now make sure that when a valid SYN arrives shortly thereafter
+// (with the same address 4-tuple) we can still successfully establish
+// a connection.
+
+0.200 < S 0:0(0) win 65535 <mss 1460,sackOK,nop,nop,nop,wscale 7>
+0.200 > S. 0:0(0) ack 1 <...>
+
+0.300 < . 1:1(0) ack 1 win 65535
+0.300 accept(3, ..., ...) = 4