From 502e89f4ad7ede50634c74577859732e5b8d0428 Mon Sep 17 00:00:00 2001
From: goldsimon <goldsimon>
Date: Fri, 16 Oct 2009 21:07:48 +0000
Subject: [PATCH] Fixed bug #27315: zero window probe and FIN

---
 CHANGELOG          |  3 +++
 src/core/tcp_out.c | 17 +++++++++++++----
 2 files changed, 16 insertions(+), 4 deletions(-)

diff --git a/CHANGELOG b/CHANGELOG
index 7afb3268..4c99bfcd 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -43,6 +43,9 @@ HISTORY
 
   ++ Bugfixes:
 
+  2009-10-16: Simon Goldschmidt
+  * tcp_out.c: Fixed bug #27315: zero window probe and FIN
+
   2009-10-16: Simon Goldschmidt
   * ip.c: Fixed bug #27390: Source IP check in ip_input() causes it to drop
     valid DHCP packets -> allow 0.0.0.0 as source address when LWIP_DHCP is
diff --git a/src/core/tcp_out.c b/src/core/tcp_out.c
index bef38b26..60d0f87b 100644
--- a/src/core/tcp_out.c
+++ b/src/core/tcp_out.c
@@ -926,6 +926,8 @@ tcp_zero_window_probe(struct tcp_pcb *pcb)
   struct pbuf *p;
   struct tcp_hdr *tcphdr;
   struct tcp_seg *seg;
+  u16_t len;
+  u8_t is_fin;
 
   LWIP_DEBUGF(TCP_DEBUG, 
               ("tcp_zero_window_probe: sending ZERO WINDOW probe to %"
@@ -946,8 +948,10 @@ tcp_zero_window_probe(struct tcp_pcb *pcb)
   if(seg == NULL)
     return;
 
-  p = pbuf_alloc(PBUF_IP, TCP_HLEN + 1, PBUF_RAM);
-   
+  is_fin = (TCPH_FLAGS(seg->tcphdr) & TCP_FIN) != 0;
+  len = is_fin ? TCP_HLEN : TCP_HLEN + 1;
+
+  p = pbuf_alloc(PBUF_IP, len, PBUF_RAM);
   if(p == NULL) {
     LWIP_DEBUGF(TCP_DEBUG, ("tcp_zero_window_probe: no memory for pbuf\n"));
     return;
@@ -957,8 +961,13 @@ tcp_zero_window_probe(struct tcp_pcb *pcb)
 
   tcphdr = tcp_output_set_header(pcb, p, 0, seg->tcphdr->seqno);
 
-  /* Copy in one byte from the head of the unacked queue */
-  *((char *)p->payload + sizeof(struct tcp_hdr)) = *(char *)seg->dataptr;
+  if (is_fin) {
+    /* FIN segment, no data */
+    TCPH_FLAGS_SET(tcphdr, TCP_ACK | TCP_FIN);
+  } else {
+    /* Data segment, copy in one byte from the head of the unacked queue */
+    *((char *)p->payload + sizeof(struct tcp_hdr)) = *(char *)seg->dataptr;
+  }
 
 #if CHECKSUM_GEN_TCP
   tcphdr->chksum = inet_chksum_pseudo(p, &pcb->local_ip, &pcb->remote_ip,