From f70c3c1f4ec1c65683a6fc107cfe438bb193a935 Mon Sep 17 00:00:00 2001
From: Michael Tuexen <tuexen@fh-muenster.de>
Date: Mon, 17 Sep 2018 20:28:00 +0200
Subject: [PATCH] Improve rebustness for TCP connection teardown.
When tearing down a TCP connection, try injecting a RST segment
by pretending to peer has received the last packet as an out of
the blue packet.
---
gtests/net/packetdrill/run_packet.c | 54 ++++++++++++++---------------
gtests/net/packetdrill/socket.h | 1 +
2 files changed, 27 insertions(+), 28 deletions(-)
diff --git a/gtests/net/packetdrill/run_packet.c b/gtests/net/packetdrill/run_packet.c
index 549dab7d..9038cedb 100644
--- a/gtests/net/packetdrill/run_packet.c
+++ b/gtests/net/packetdrill/run_packet.c
@@ -3211,6 +3211,7 @@ static int do_outbound_script_packet(
/* Save the TCP header so we can reset the connection at the end. */
if (live_packet->tcp) {
socket->last_outbound_tcp_header = *(live_packet->tcp);
+ socket->last_outbound_tcp_payload_len = packet_payload_len(live_packet);
if (live_packet->flags & FLAGS_UDP_ENCAPSULATED) {
struct udp *udp = (struct udp *)(live_packet->tcp) - 1;
@@ -3508,12 +3509,12 @@ int reset_connection(struct state *state, struct socket *socket)
{
char *error = NULL;
u32 seq = 0, ack_seq = 0;
- u16 window = 0;
struct packet *packet = NULL;
struct tuple live_inbound;
int result = STATUS_OK;
u16 udp_src_port;
u16 udp_dst_port;
+ bool ack_bit;
if (socket->last_outbound_udp_encaps_src_port != 0 ||
socket->last_outbound_udp_encaps_dst_port != 0) {
@@ -3524,38 +3525,35 @@ int reset_connection(struct state *state, struct socket *socket)
udp_dst_port = socket->last_injected_udp_encaps_dst_port;
}
/* Pick TCP header fields to be something the kernel will accept. */
- if (socket->last_injected_tcp_header.ack) {
- /* If we've already injected something, then use a sequence
- * number right after the last one we injected, and ACK
- * the last thing we ACKed, and offer the same receive
- * window we last offered.
- */
- seq = (ntohl(socket->last_injected_tcp_header.seq) +
- (socket->last_injected_tcp_header.syn ? 1 : 0) +
- (socket->last_injected_tcp_header.fin ? 1 : 0) +
- socket->last_injected_tcp_payload_len);
- ack_seq = ntohl(socket->last_injected_tcp_header.ack_seq);
- window = ntohs(socket->last_injected_tcp_header.window);
- } else if (socket->last_outbound_tcp_header.ack) {
- /* If the kernel ACKed something, then just make sure
- * we use the sequence number it ACKed, which will be
- * something it expects.
- */
- seq = ntohl(socket->last_outbound_tcp_header.ack_seq);
- ack_seq = ntohl(socket->last_outbound_tcp_header.seq);
+ if (socket->last_outbound_tcp_header.doff > 0) {
+ /* The kernel has sent something. */
+ if (socket->last_outbound_tcp_header.ack) {
+ seq = ntohl(socket->last_outbound_tcp_header.ack_seq);
+ ack_seq = 0;
+ ack_bit = false;
+ } else {
+ seq = 0;
+ ack_seq = (ntohl(socket->last_outbound_tcp_header.seq) +
+ (socket->last_outbound_tcp_header.syn ? 1 : 0) +
+ (socket->last_outbound_tcp_header.fin ? 1 : 0) +
+ socket->last_outbound_tcp_payload_len);
+ ack_bit = true;
+ }
+ } else if (socket->last_injected_tcp_header.doff > 0) {
+ /* The kernel hasn't sent anything, but a packet was injected */
+ seq = (ntohl(socket->last_injected_tcp_header.seq) +
+ (socket->last_injected_tcp_header.syn ? 1 : 0) +
+ (socket->last_injected_tcp_header.fin ? 1 : 0) +
+ socket->last_injected_tcp_payload_len);
+ ack_seq = 0;
+ ack_bit = false;
} else {
- /* If the kernel didn't ACK anything, then it probably
- * sent only an initial SYN. So we get to send any
- * sequence number we want, but should send an ACK
- * suggesting we've seen the kernel's SYN.
- */
- seq = 0;
- ack_seq = ntohl(socket->last_outbound_tcp_header.seq) + 1;
+ return result;
}
packet = new_tcp_packet(socket->address_family,
DIRECTION_INBOUND, ECN_NONE,
- "R.", seq, 0, ack_seq, window, NULL, false, false,
+ ack_bit ? "R." : "R", seq, 0, ack_seq, 0, NULL, false, false,
false, false, udp_src_port, udp_dst_port, &error);
if (packet == NULL)
die("%s", error);
diff --git a/gtests/net/packetdrill/socket.h b/gtests/net/packetdrill/socket.h
index 0012903d..7cbdfded 100644
--- a/gtests/net/packetdrill/socket.h
+++ b/gtests/net/packetdrill/socket.h
@@ -113,6 +113,7 @@ struct socket {
* order to induce the kernel to free the socket.
*/
struct tcp last_outbound_tcp_header;
+ u32 last_outbound_tcp_payload_len;
struct tcp last_injected_tcp_header;
u32 last_injected_tcp_payload_len;
--
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