Re: [Qemu-devel] [PATCH 5/10] Add network announce function

Anthony Liguori
2008-09-10T13:55:29Z

Chris Lalancette wrote:
> Anthony Liguori wrote:
>
>> +static int announce_self_create(uint8_t *buf,
>> + uint8_t *mac_addr)
>> +{
>> + uint32_t magic = EXPERIMENTAL_MAGIC;
>> + uint16_t proto = htons(ETH_P_EXPERIMENTAL);
>> +
>> + /* FIXME: should we send a different packet (arp/rarp/ping)? */
>> +
>> + memset(buf, 0xff, 6); /* h_dst */
>> + memcpy(buf + 6, mac_addr, 6); /* h_src */
>> + memcpy(buf + 12, &proto, 2); /* h_proto */
>> + memcpy(buf + 14, &magic, 4); /* magic */
>> +
>> + return 18; /* len */
>> +}
>> +
>> +void qemu_announce_self(void)
>> +{
>> + int i, j, len;
>> + VLANState *vlan;
>> + VLANClientState *vc;
>> + uint8_t buf[256];
>> +
>> + for (i = 0; i < nb_nics; i++) {
>> + 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);
>> + }
>> + }
>> +}
>> +
>>
>
> This one is yucky, as the FIXME points out. First, I'm guessing the point of
> this is to do an ARP poison on the switch? If so, we probably want to do some
> kind of ARP packet, although I'm not an expert on this. Also, why are we trying
> SELF_ANNOUNCE_ROUNDS times? Is there some issue where some of these get
> dropped, or is it just being safe about it?
>

I didn't write this code originally. Perhaps Uri or Avi know who did
and can provide some insight?

Regards,

Anthony Liguori

> Chris Lalancette
>
>