Delayed IP packets

In the current implementation, if Slirp tries to send an IP packet to a client
with an unknown hardware address, the packet is simply dropped and an ARP
request is sent (if_encap in slirp/slirp.c).

With this patch, Slirp will send the ARP request, re-queue the packet and try
to send it later. The packet is dropped after one second if the ARP reply is
not received.

Signed-off-by: Fabien Chouteau <chouteau@adacore.com>
Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>

1 files changed, 24 insertions, 4 deletions

diff --git a/slirp/if.c b/slirp/if.c
index 0f04e13..2d79e45 100644
--- a/slirp/if.c
+++ b/slirp/if.c
@@ -6,6 +6,7 @@
  */
 
 #include <slirp.h>
+#include "qemu-timer.h"
 
 #define ifs_init(ifm) ((ifm)->ifs_next = (ifm)->ifs_prev = (ifm))
 
@@ -105,6 +106,9 @@ if_output(struct socket *so, struct mbuf *ifm)
 	ifs_init(ifm);
 	insque(ifm, ifq);
 
+        /* Expiration date = Now + 1 second */
+        ifm->expiration_date = qemu_get_clock_ns(rt_clock) + 1000000000ULL;
+
 diddit:
 	slirp->if_queued++;
 
@@ -153,6 +157,9 @@ diddit:
 void
 if_start(Slirp *slirp)
 {
+    int requeued = 0;
+    uint64_t now;
+
 	struct mbuf *ifm, *ifqt;
 
 	DEBUG_CALL("if_start");
@@ -165,6 +172,8 @@ if_start(Slirp *slirp)
         if (!slirp_can_output(slirp->opaque))
             return;
 
+        now = qemu_get_clock_ns(rt_clock);
+
 	/*
 	 * See which queue to get next packet from
 	 * If there's something in the fastq, select it immediately
@@ -199,11 +208,22 @@ if_start(Slirp *slirp)
 		   ifm->ifq_so->so_nqueued = 0;
 	}
 
-	/* Encapsulate the packet for sending */
-        if_encap(slirp, (uint8_t *)ifm->m_data, ifm->m_len);
-
-        m_free(ifm);
+        if (ifm->expiration_date < now) {
+            /* Expired */
+            m_free(ifm);
+        } else {
+            /* Encapsulate the packet for sending */
+            if (if_encap(slirp, ifm)) {
+                m_free(ifm);
+            } else {
+                /* re-queue */
+                insque(ifm, ifqt);
+                requeued++;
+            }
+        }
 
 	if (slirp->if_queued)
 	   goto again;
+
+        slirp->if_queued = requeued;
 }