issue: 2246994 Set proper FIN/RST flags for split segments

When a segment with FIN flag is split into multiple segments, the leftmost segment retains all its flags including FIN. This leads to corrupted TCP stream. To fix this, move FIN/RST flags to the rightmost among the split segments. Currently, VMA doesn't support RST flag in the pending segments, however, it may be changed in the future. Signed-off-by: Dmytro Podgornyi <[email protected]>
Mellanox · Mar 10, 2021 · b8a3a9e · b8a3a9e
1 parent da44080
commit b8a3a9e
Showing 1 changed file with 16 additions and 0 deletions.
diff --git a/src/vma/lwip/tcp_out.c b/src/vma/lwip/tcp_out.c
@@ -965,6 +965,17 @@ tcp_send_empty_ack(struct tcp_pcb *pcb)
   return ERR_OK;
 }
 
+/* Used by split functions to move FIN/RST flags to the rightmost segment. */
+static void tcp_seg_move_flags(struct tcp_seg *from, struct tcp_seg *to, u8_t flags)
+{
+  u16_t from_flags = TCPH_FLAGS(from->tcphdr) & flags;
+
+  if ((from != to) && (to != NULL) && from_flags) {
+    TCPH_SET_FLAG(to->tcphdr, from_flags);
+    TCPH_UNSET_FLAG(from->tcphdr, flags);
+  }
+}
+
 #if LWIP_TSO
 /**
  * Called by tcp_output() to actually join few following TCP segments
@@ -1130,6 +1141,7 @@ tcp_split_one_segment(struct tcp_pcb *pcb, struct tcp_seg *seg, u32_t lentosend,
     pcb->unsent_oversize = result ? oversize : 0;
 #endif /* TCP_OVERSIZE */
   }
+  tcp_seg_move_flags(seg, cur_seg, TCP_FIN | TCP_RST);
   return result;
 }
 
@@ -1229,6 +1241,8 @@ tcp_rexmit_segment(struct tcp_pcb *pcb, struct tcp_seg *seg, u32_t wnd)
 #endif /* TCP_OVERSIZE */
     }
 
+    tcp_seg_move_flags(cur_seg, new_seg, TCP_FIN | TCP_RST);
+
     if (NULL == tcp_split_one_segment(pcb, cur_seg, mss_local, optflags, optlen)) {
         LWIP_DEBUGF(TCP_OUTPUT_DEBUG | 2, ("tcp_split_one_segment: could not allocate memory for segment\n"));
         if (new_seg->len > pcb->mss) {
@@ -1400,6 +1414,8 @@ tcp_split_segment(struct tcp_pcb *pcb, struct tcp_seg *seg, u32_t wnd)
     LWIP_ASSERT("tcp_split_segment: We should not be here [else]",0);
   }
 
+  tcp_seg_move_flags(seg, newseg, TCP_FIN | TCP_RST);
+
 #if TCP_TSO_DEBUG
   LWIP_DEBUGF(TCP_TSO_DEBUG | LWIP_DBG_TRACE,
                 ("tcp_split:  max: %-5d unsent %s\n",