Remove PIPEXCSESSION pipex(4) ioctl(2) command from kernel and man page.

Long time ago pipex(4) session can't be deleted until both pipex(4)
input and output queues become empty. Dead sessions were linked to the
stack and the `ip_forward' flag was used to prevent packets forwarding.
npppd(8) marked such sessions by doing PIPEXCSESSION ioctl(2) call.

But since we started to unlink close session from the stack, this logic
became unnecessary. Also pipex(4) session could be closed just after
close request.

npppd(8) was the only userland program which did PIPEXCSESSION ioctl(2)
call, and we removed it week ago. It's time to remove the remains.

Now the `flags' member of 'pipex_session' structure became immutable.

ok yasuoka@

Remove PIPEX{S,G}MODE ioctl(2) commands. This time they are pretty dummy
and were kept only for backward compatibility reasons.

ok mpi@ yasuoka@

Some times ago we disabled in-kernel timeout for pppx(4) related
pipex(4) sessions. We did this for prevent use after free issue caused
by pipex_timer(). By default "idle-timeout" is not set in
npppd.conf(5) and I guess this is reason for we forgot to describe this
exception in npppd.conf(5).

Since it's pppx(4) related bug description was added to BUGS section of
pppx(4) man page.

npppd.conf(5) has this exception described in "idle-timeout" section.

ok jmc@ yasuoka@

tun(4) has been replaced by pppac(4), from Vitaliy Makkoveev.

Including sys/types.h and net/if.h are needed to use pipex(4).

typos: mastter -> master, mandoatory -> mandatory.

convert .Fd #include to .In

Fix the links to pppx(4).

diff from Fabian Raetz.

Add a missing .An macro.
Found by Enrico <Camarda at amnz dot org>
during the BSDCan Doc Sprint.

PPP not Ppp

Add pppx.4 and enable links to it.

ok dlg@

typo in #include

tweak previous;

don't use link to npppd(8) and pppx(4) until they are ready.

add pipex(4) man page.

Remove PIPEX{S,G}MODE ioctl(2) commands. This time they are pretty dummy
and were kept only for backward compatibility reasons.

ok mpi@ yasuoka@

Some times ago we disabled in-kernel timeout for pppx(4) related
pipex(4) sessions. We did this for prevent use after free issue caused
by pipex_timer(). By default "idle-timeout" is not set in
npppd.conf(5) and I guess this is reason for we forgot to describe this
exception in npppd.conf(5).

Since it's pppx(4) related bug description was added to BUGS section of
pppx(4) man page.

npppd.conf(5) has this exception described in "idle-timeout" section.

ok jmc@ yasuoka@

tun(4) has been replaced by pppac(4), from Vitaliy Makkoveev.

Including sys/types.h and net/if.h are needed to use pipex(4).

typos: mastter -> master, mandoatory -> mandatory.

convert .Fd #include to .In

Fix the links to pppx(4).

diff from Fabian Raetz.

Add a missing .An macro.
Found by Enrico <Camarda at amnz dot org>
during the BSDCan Doc Sprint.

PPP not Ppp

Add pppx.4 and enable links to it.

ok dlg@

typo in #include

tweak previous;

don't use link to npppd(8) and pppx(4) until they are ready.

add pipex(4) man page.

Some times ago we disabled in-kernel timeout for pppx(4) related
pipex(4) sessions. We did this for prevent use after free issue caused
by pipex_timer(). By default "idle-timeout" is not set in
npppd.conf(5) and I guess this is reason for we forgot to describe this
exception in npppd.conf(5).

Since it's pppx(4) related bug description was added to BUGS section of
pppx(4) man page.

npppd.conf(5) has this exception described in "idle-timeout" section.

ok jmc@ yasuoka@

tun(4) has been replaced by pppac(4), from Vitaliy Makkoveev.

Including sys/types.h and net/if.h are needed to use pipex(4).

typos: mastter -> master, mandoatory -> mandatory.

convert .Fd #include to .In

Fix the links to pppx(4).

diff from Fabian Raetz.

Add a missing .An macro.
Found by Enrico <Camarda at amnz dot org>
during the BSDCan Doc Sprint.

PPP not Ppp

Add pppx.4 and enable links to it.

ok dlg@

typo in #include

tweak previous;

don't use link to npppd(8) and pppx(4) until they are ready.

add pipex(4) man page.

tun(4) has been replaced by pppac(4), from Vitaliy Makkoveev.

Including sys/types.h and net/if.h are needed to use pipex(4).

typos: mastter -> master, mandoatory -> mandatory.

convert .Fd #include to .In

Fix the links to pppx(4).

diff from Fabian Raetz.

Add a missing .An macro.
Found by Enrico <Camarda at amnz dot org>
during the BSDCan Doc Sprint.

PPP not Ppp

Add pppx.4 and enable links to it.

ok dlg@

typo in #include

tweak previous;

don't use link to npppd(8) and pppx(4) until they are ready.

add pipex(4) man page.

Including sys/types.h and net/if.h are needed to use pipex(4).

typos: mastter -> master, mandoatory -> mandatory.

convert .Fd #include to .In

Fix the links to pppx(4).

diff from Fabian Raetz.

Add a missing .An macro.
Found by Enrico <Camarda at amnz dot org>
during the BSDCan Doc Sprint.

PPP not Ppp

Add pppx.4 and enable links to it.

ok dlg@

typo in #include

tweak previous;

don't use link to npppd(8) and pppx(4) until they are ready.

add pipex(4) man page.