On 26/08/2022 01.15, Peter Delevoryas wrote:
On Fri, Aug 26, 2022 at 12:56:10AM +0200, Samuel Thibault wrote:
Hello,
Peter Delevoryas, le jeu. 25 août 2022 15:38:53 -0700, a ecrit:
It seems like there's support for an IPv6 dns proxy, and there's literally a
file called "dhcpv6.c" in slirp, but it has a comment saying it only supports
whatever is necessary for TFTP network boot I guess.
For which DNS support is welcome :)
Maybe there's no support then?
It seems there is:
if (ri.want_dns) {
*resp++ = OPTION_DNS_SERVERS >> 8; /* option-code high byte */
*resp++ = OPTION_DNS_SERVERS; /* option-code low byte */
*resp++ = 0; /* option-len high byte */
*resp++ = 16; /* option-len low byte */
memcpy(resp, &slirp->vnameserver_addr6, 16);
resp += 16;
}
Well, that's great, but actually I just care about whether slirp supports DHCPv6
address requests. Sorry if I didn't explain that properly.
My goal is to run:
qemu-system-arm -machine fby35-bmc -nographic -mtdblock image-bmc \
-net nic,model=ftgmac100,netdev=nic \
-netdev user,id=nic,hostfwd=::2222-:22
And then see that the BMC received an IPv6 address assignment.
But, slirp currently just supports IP address assignment through BOOTP? I
didn't realize that until looking a little closer at the code.
No, slirp support "IPv6 *stateless* address assignment" (if you haven't
heard about that before, I suggest to google it). That means that IPv6
addresses are not administered by a DHCP server, but that each client can
built its own IPv6 address. It basically works like this (don't quote me on
that, it's been a while since I worked with this stuff): Once the network
interface of the client gets activated, the OS creates a link-local IPv6
that can be only used for activating on the link (based on the MAC address).
It then uses this address for sending a "router solicitation" message, and
if there is a router on the link, it replies with a "router advertisment"
that contains a routable prefix. The client then can take this prefix to
form a unique IPv6 address and assign it to its interface. QEMU/slirp
support this way of address assignment, see ndp_send_na() in ip6_icmp.c.
So if your BMC code supports stateless IPv6 address (it certainly should),
you should be fine already).
HTH,
Thomas
