Date: Fri, 10 Jan 1997 12:02:01 -0100 From: "Brian Somers" <brian.somers@utell.net> To: <dhcp-dist@wide.ad.jp> Cc: <brian@awfulhak.demon.co.uk>, <hackers@freebsd.org> Subject: (wide) DHCP negotiation using the REQUEST_IPADDR option Message-ID: <199701101202.MAA10949@ui-gate.utell.co.uk>
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I seem to have found a problem with dhcp-1.3beta when DHCP'ing for a
windows 95 box (I have little experience, so I don't know if it's just
win95).
Under windows 95, the dhcp request is sent with the REQUEST_IPADDR option
set. Dhcps will try to select an IP address based on the CID before the
requested IP, calling select_wcid() from request() in server/dhcps.c. If
it finds a match, *and* it has a REQUEST_IPADDR option (reqip.s_addr) that
differs from the entry found (res->ip_addr->s_addr), it returns(-1) - not
replying to the request.
If however, a NAK is returned, the client (win95) will do another dhcp
request without the REQUEST_IPADDR option set..... voila IP address
altered.
I'm not sure about the original logic behind returning -1 above.
If anyone's interested in reproducing this, make sure that you delete the
arp entry on the server box while the win95 box is shut down..... I wasted
a lot of time here !
The (trivial) patch is attached. Note, the freebsd port does not affect
this (nor do I know if patches have been submitted for freebsd), although
line numbers are probably different.
Brian <brian@awfulhak.demon.co.uk> <brian@freebsd.org>
Don't __EVER__ lose your sense of humour
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*** dhcps.c.orig Fri Jan 10 11:45:26 1997
--- dhcps.c Fri Jan 10 11:48:57 1997
***************
*** 1586,1594 ****
res = NULL;
res = select_wcid(DHCPREQUEST, &cid, curr_epoch);
! if (res != NULL && res->ip_addr != NULL &&
! res->ip_addr->s_addr == reqip.s_addr)
! goto ack;
else if (reqforme == 1)
goto nak;
else
--- 1586,1596 ----
res = NULL;
res = select_wcid(DHCPREQUEST, &cid, curr_epoch);
! if (res != NULL && res->ip_addr != NULL)
! if (res->ip_addr->s_addr == reqip.s_addr)
! goto ack;
! else
! goto nak;
else if (reqforme == 1)
goto nak;
else
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