Re: [PATCH v4 2/4] util/qemu-sockets.c: Split host:port parsing out of inet_parse

[Samuel Thibault <samuel.thibault@gnu.org>]

Hello,

Doug Evans, le ven. 05 mars 2021 17:00:13 -0800, a ecrit:
> Is it possible for QEMU to lazily determine the guest's IPv6
> address? I.e., postpone the ""->guest address mapping until it's
> needed and then, say, take the first entry in the NDP table?

That would probably be possible, yes, by moving the 

if (!guest_addr.s_addr) {
    guest_addr = slirp->vdhcp_startaddr;
}

from slirp_add_hostfwd() and alike to tcp_connect() and sorecvfrom()
(along the other sotranslate call).

> That feels a bit fragile: what if someone else gets the first entry in
> the NDP table? But is that any more fragile than assuming the first
> handed out DHCP address is to the guest?

I don't think it's really more fragile.

> [<<-- Honest question, can we assume the first handed out DHCP address
> will necessarily be the guest?]

It "cannot" be anything else. What could happen is a PXE loader that
uses DHCP/NDP, and then the OS that does it again.

> But that would mean the defaults for the guest would have to be
> different than for the host. E.g.,
> host: ",ipv4" means both,

Why would it mean both? I don't follow you here.

> whereas guest: ",ipv4" (ideally) means ipv4 (since both is meaningless)

Samuel