Re: [Qemu-devel] [PATCH] [tftp] Handle TFTP ERROR from client

[Anthony Liguori]

On 01/07/2010 11:01 AM, Thomas Horsten wrote:

If a PXE client only wants to find out the size of a file, it will
open the file and then abort the transfer by sending a TFTP ERROR packet.

The ERROR packet should cause qemu to terminate the session. If not,
the sessions will soon run out and cause timeouts in the client.

Also, if a TFTP session already exists with same IP/UDP port, it
should be terminated when a new RRQ is received, instead of creating a
duplicate (which will never be used).

A patch for gPXE to send the ERROR packet is also being submitted to
gPXE. Together they resolve slowness/hanging when booting pxegrub from
qemu's internal TFTP server. The patch from Milan Plzik to return
after sending OACK is also required for a complete fix.

Signed-off-by: Thomas Horsten<tho...@horsten.com>
Signed-off-by: Milan Plzik<milan.pl...@gmail.com>

Applied.  Thanks.

Regards,

Anthony Liguori

---
  slirp/tftp.c |   23 +++++++++++++++++++++++
  1 files changed, 23 insertions(+), 0 deletions(-)

diff --git a/slirp/tftp.c b/slirp/tftp.c
index db869fc..96c0e0c 100644
--- a/slirp/tftp.c
+++ b/slirp/tftp.c
@@ -264,6 +264,12 @@ static void tftp_handle_rrq(Slirp *slirp, struct tftp_t 
*tp, int pktlen)
    size_t prefix_len;
    char *req_fname;

+  /* check if a session already exists and if so terminate it */
+  s = tftp_session_find(slirp, tp);
+  if (s>= 0) {
+    tftp_session_terminate(&slirp->tftp_sessions[s]);
+  }
+
    s = tftp_session_allocate(slirp, tp);

    if (s<  0) {
@@ -386,6 +392,19 @@ static void tftp_handle_ack(Slirp *slirp, struct tftp_t 
*tp, int pktlen)
    }
  }

+static void tftp_handle_error(Slirp *slirp, struct tftp_t *tp, int pktlen)
+{
+  int s;
+
+  s = tftp_session_find(slirp, tp);
+
+  if (s<  0) {
+    return;
+  }
+
+  tftp_session_terminate(&slirp->tftp_sessions[s]);
+}
+
  void tftp_input(struct mbuf *m)
  {
    struct tftp_t *tp = (struct tftp_t *)m->m_data;
@@ -398,5 +417,9 @@ void tftp_input(struct mbuf *m)
    case TFTP_ACK:
      tftp_handle_ack(m->slirp, tp, m->m_len);
      break;
+
+  case TFTP_ERROR:
+    tftp_handle_error(m->slirp, tp, m->m_len);
+    break;
    }
  }