Xen devel - Jan 2009 - [PATCH 1/1] qemu-dm: send arp like packets for hvm live migration

Subject: qemu-dm: send arp like packets for hvm live migration

When two servers connect different switch/hub and do live migration 
between them, network connect will no reponse about 30 seconds,
it caused by migration finished, target server do not broadcast
guest os''s network info.

In pvm, when backend changed, netfront driver will send fake arp
to network, so, hvm also need this.

Uri Lublin have write the patch for it:
http://www.mail-archive.com/qemu-devel@nongnu.org/msg09306.html

I add send arp like packets at tap_receive(), and it looked like
work fine.

Regards,
Joe

Signed-off-by: Joe Jin <joe.jin@oracle.com>
Tested-by: Deepak Patel <deepak.patel@oracle.com>
CC: Keir Fraser <keir.fraser@eu.citrix.com>
CC: Kurt C. Hackel <kurt.hackel@oracle.com>
---

 vl.c |   65 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 65 insertions(+)

--- a/tools/ioemu/vl.c	2008-12-22 10:24:03.000000000 +0800
+++ b/tools/ioemu/vl.c	2008-12-22 15:38:27.000000000 +0800
@@ -57,6 +57,9 @@
 #include <linux/ppdev.h>
 #endif
 #endif
+#if defined(__linux__)
+#include <linux/if_ether.h>
+#endif
 #endif
 
 #if defined(CONFIG_SLIRP)
@@ -3163,10 +3166,22 @@ typedef struct TAPState {
     int fd;
 } TAPState;
 
+static void qemu_tap_announce_self(void);
+
 static void tap_receive(void *opaque, const uint8_t *buf, int size)
 {
+    static int arp_state = 0;
     TAPState *s = opaque;
     int ret;
+
+    if (!arp_state ) {
+        arp_state = 1;
+        /* send arp like package to vlan when enter is the first.
+           for xen migration.
+        */
+        qemu_tap_announce_self();
+    }
+
     for(;;) {
         ret = write(s->fd, buf, size);
         if (ret < 0 && (errno == EINTR || errno == EAGAIN)) {
@@ -3261,6 +3276,56 @@ static int tap_open(char *ifname, int if
 }
 #endif
 
+#if defined(__linux__)
+#define SELF_ANNOUNCE_ROUNDS 5
+#define ETH_P_EXPERIMENTAL 0x01F1 /* just a number in experimental range */
+#define EXPERIMENTAL_MAGIC 0xf1f23f4f
+static int announce_self_create(unsigned char *buf, 
+                         unsigned char mac_addr[ETH_ALEN])
+{
+    struct ethhdr *eh = (struct ethhdr*)buf;
+    uint32_t *magic   = (uint32_t*)(eh+1);
+    unsigned char *p  = (unsigned char*)(magic + 1);
+
+    /* ethernet header */
+    memset(eh->h_dest,   0xff,     ETH_ALEN);
+    memcpy(eh->h_source, mac_addr, ETH_ALEN);
+    eh->h_proto = htons(ETH_P_EXPERIMENTAL);
+
+    /* magic data */
+    *magic = EXPERIMENTAL_MAGIC;
+
+    return p - buf; /* sizeof(*eh) + sizeof(*magic) */
+}
+
+static void qemu_tap_announce_self(void)
+{
+    int i, j, len;
+    VLANState *vlan;
+    VLANClientState *vc;
+    uint8_t buf[256];
+
+    for (i=0; i<nb_nics; i++) {     /* for all nics */
+        fprintf(logfile, "Send fake arp for domain %d, MAC:
[%02X:%02X:%02X:%02X:%02X:%02X]\n",
+                          domid, nd_table[i].macaddr[0], 
+                          nd_table[i].macaddr[1], nd_table[i].macaddr[2], 
+                          nd_table[i].macaddr[3], nd_table[i].macaddr[4], 
+                          nd_table[i].macaddr[5]);
+        len = announce_self_create(buf, nd_table[i].macaddr);
+        vlan = nd_table[i].vlan;
+        for(vc = vlan->first_client; vc != NULL; vc = vc->next) {
+            if (vc->fd_read == tap_receive) { /* send only if tap */
+                for (j=0; j<SELF_ANNOUNCE_ROUNDS ; j++) {
+                    vc->fd_read(vc->opaque, buf, len);
+                }
+            }
+        } /* for vc -- look for tap_receive */
+    } /* for i -- all nics */
+}
+#else
+static void qemu_tap_announce_self(void) {}
+#endif
+
 static int net_tap_init(VLANState *vlan, const char *ifname1,
                         const char *setup_script, const char *bridge)
 {


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