[Openvpn-devel,v2,3/4] Avoid reserving one more address at pool end

Message ID 20191113100702.6863-3-tom.ty89@gmail.com
State New
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Series
  • [Openvpn-devel,v2,1/4] Avoid repeating code for tap and tun+subnet in server directive
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Commit Message

Tom Yan Nov. 13, 2019, 10:07 a.m.
It appears to be a copy-and-paste kind of typo (pool start is network address + 2).
---
 src/openvpn/helper.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Comments

Tom Yan Nov. 13, 2019, 11:41 a.m. | #1
If it isn't a typo, I wonder if it is the equivalence of
`pool_end_reserve`. As with the subnet topology, each client takes up
1 address in contrast to 4 with net30.

So perhaps the question is, what's the purpose of pool_end_reserve?

On Wed, 13 Nov 2019 at 18:07, Tom Yan <tom.ty89@gmail.com> wrote:
>
> It appears to be a copy-and-paste kind of typo (pool start is network address + 2).
> ---
>  src/openvpn/helper.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/src/openvpn/helper.c b/src/openvpn/helper.c
> index 5b2ca0cc..6e2f0891 100644
> --- a/src/openvpn/helper.c
> +++ b/src/openvpn/helper.c
> @@ -349,7 +349,7 @@ helper_client_server(struct options *o)
>              {
>                  o->ifconfig_pool_defined = true;
>                  o->ifconfig_pool_start = o->server_network + ptp + 1;
> -                o->ifconfig_pool_end = (o->server_network | ~o->server_netmask) - ptp * 2;
> +                o->ifconfig_pool_end = (o->server_network | ~o->server_netmask) - ptp;
>                  ifconfig_pool_verify_range(M_USAGE, o->ifconfig_pool_start, o->ifconfig_pool_end);
>              }
>              o->ifconfig_pool_netmask = o->server_netmask;
> --
> 2.24.0
>
Tom Yan Nov. 13, 2019, 2:33 p.m. | #2
So a recent question on the openvpn-users caused me to have found
that, this "reserve-one-more-address" is seemingly related to Windows
/ --ip-win32. Commit 251cc8f made a "correction" to the
manual/documentation which sort of implied that the address is
reserved as the default address chosen by `--ip-win32 dynamic` as DHCP
server (when `dev` is a tun).

But the thing is, the choice can be made by user with an extra
parameter (`offset`) that does not affect the --ifconfig-pool set by
--server. So as far as I can see here, it *implies* that the server
directive shouldn't be used with `--ip-win32 dynamic offset`. (This is
pretty nasty to me, although it might practically be convenient to the
"default lovers").

I am not sure what to do with this. Personally I prefer ditching the
reservation and simply note that `--ip-win32 dynamic` shouldn't be
used with `--server`, for simplicity and consistency. (In addition to
the consistency of whether --server can be used with `--ip-win32
dynamic`, x.x.x.254 may actually be used in a tap set-up, rendering
commit 251cc8f "wrong".

On Wed, 13 Nov 2019 at 19:41, Tom Yan <tom.ty89@gmail.com> wrote:
>
> If it isn't a typo, I wonder if it is the equivalence of
> `pool_end_reserve`. As with the subnet topology, each client takes up
> 1 address in contrast to 4 with net30.
>
> So perhaps the question is, what's the purpose of pool_end_reserve?
>
> On Wed, 13 Nov 2019 at 18:07, Tom Yan <tom.ty89@gmail.com> wrote:
> >
> > It appears to be a copy-and-paste kind of typo (pool start is network address + 2).
> > ---
> >  src/openvpn/helper.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/src/openvpn/helper.c b/src/openvpn/helper.c
> > index 5b2ca0cc..6e2f0891 100644
> > --- a/src/openvpn/helper.c
> > +++ b/src/openvpn/helper.c
> > @@ -349,7 +349,7 @@ helper_client_server(struct options *o)
> >              {
> >                  o->ifconfig_pool_defined = true;
> >                  o->ifconfig_pool_start = o->server_network + ptp + 1;
> > -                o->ifconfig_pool_end = (o->server_network | ~o->server_netmask) - ptp * 2;
> > +                o->ifconfig_pool_end = (o->server_network | ~o->server_netmask) - ptp;
> >                  ifconfig_pool_verify_range(M_USAGE, o->ifconfig_pool_start, o->ifconfig_pool_end);
> >              }
> >              o->ifconfig_pool_netmask = o->server_netmask;
> > --
> > 2.24.0
> >

Patch

diff --git a/src/openvpn/helper.c b/src/openvpn/helper.c
index 5b2ca0cc..6e2f0891 100644
--- a/src/openvpn/helper.c
+++ b/src/openvpn/helper.c
@@ -349,7 +349,7 @@  helper_client_server(struct options *o)
             {
                 o->ifconfig_pool_defined = true;
                 o->ifconfig_pool_start = o->server_network + ptp + 1;
-                o->ifconfig_pool_end = (o->server_network | ~o->server_netmask) - ptp * 2;
+                o->ifconfig_pool_end = (o->server_network | ~o->server_netmask) - ptp;
                 ifconfig_pool_verify_range(M_USAGE, o->ifconfig_pool_start, o->ifconfig_pool_end);
             }
             o->ifconfig_pool_netmask = o->server_netmask;