Re: [Qemu-devel] [PATCH 2/6] slirp: Fix assertion failure on rejected DHCP requests

[Jan Kiszka]

On 2012-02-24 01:23, David Gibson wrote:
> The guest network stack might DHCPREQUEST an address that the slirp built
> in dhcp server can't let it have - for example if the guest has an old
> leases file from another network configuration.  In this case the dhcp
> server should and does reject the request and prepares to send a DHCPNAK
> to the client.
> 
> However, in this case the daddr variable in bootp_reply() is set to
> 0.0.0.0.  Shortly afterwards, it unconditionally attempts to pre-insert the
> new client address into the ARP table.  This causes an assertion failure in
> arp_address_add() because of the 0.0.0.0 address.
> 
> According to RFC2131, DHCPNAK messages for clients on the same subnet
> must be sent to the broadcast address (S3.2, subpoint 2).
> 
> Cc: Jan Kiszka <address@hidden>
> 
> Signed-off-by: David Gibson <address@hidden>

Thanks, applied to the slirp queue.

Jan

> ---
>  slirp/bootp.c |    3 ++-
>  1 files changed, 2 insertions(+), 1 deletions(-)
> 
> diff --git a/slirp/bootp.c b/slirp/bootp.c
> index efd1fe7..64eac7d 100644
> --- a/slirp/bootp.c
> +++ b/slirp/bootp.c
> @@ -200,7 +200,8 @@ static void bootp_reply(Slirp *slirp, const struct 
> bootp_t *bp)
>              daddr.sin_addr = preq_addr;
>              memcpy(bc->macaddr, client_ethaddr, ETH_ALEN);
>          } else {
> -            daddr.sin_addr.s_addr = 0;
> +            /* DHCPNAKs should be sent to broadcast */
> +            daddr.sin_addr.s_addr = 0xffffffff;
>          }
>      } else {
>          bc = find_addr(slirp, &daddr.sin_addr, bp->bp_hwaddr);

-- 
Siemens AG, Corporate Technology, CT T DE IT 1
Corporate Competence Center Embedded Linux