Date: Sun, 12 Dec 2004 12:53:21 -0800 From: Brooks Davis <brooks@one-eyed-alien.net> To: Ken Smith <kensmith@cse.Buffalo.EDU> Cc: src-committers@FreeBSD.org Subject: Re: cvs commit: src/sbin/ifconfig ifconfig.c src/sys/net if.c if.h Message-ID: <20041212205321.GA28802@odin.ac.hmc.edu> In-Reply-To: <20041212204111.GB5503@electra.cse.Buffalo.EDU> References: <200412122012.iBCKCou6068020@repoman.freebsd.org> <20041212204111.GB5503@electra.cse.Buffalo.EDU>
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On Sun, Dec 12, 2004 at 03:41:11PM -0500, Ken Smith wrote:
> On Sun, Dec 12, 2004 at 08:12:50PM +0000, Brooks Davis wrote:
> > brooks 2004-12-12 20:12:50 UTC
> >=20
> > FreeBSD src repository
> >=20
> > Modified files: (Branch: RELENG_4)
> > sbin/ifconfig ifconfig.c=20
> > sys/net if.c if.h=20
> > Log:
> > MFC the addition of ifi_datalen to struct if_data and ifconfig support
> > for it. The change to struct if_data differs slightly from the one in
> > 5.3 in that a pad is added after ifi_xmitquota rather then adding
> > ifi_link_state before ifi_recvquota. This is necessicary to maintain
> > the 4.x ABI.
> > =20
> > Revision Changes Path
> > 1.51.2.23 +4 -1 src/sbin/ifconfig/ifconfig.c
> > 1.85.2.28 +2 -0 src/sys/net/if.c
> > 1.58.2.12 +2 -0 src/sys/net/if.h
>=20
> In if.h you are adding new fields that didn't exist before:
>=20
> #ifndef _NET_IF_H_
> @@ -97,6 +97,8 @@ struct if_data {
> u_char ifi_hdrlen; /* media header length */
> u_char ifi_recvquota; /* polling quota for receive intrs */
> u_char ifi_xmitquota; /* polling quota for xmit intrs */
> + u_char ifi_do_no_use; /* pad for ifi_datalen's position */
> + u_char ifi_datalen; /* length of this data struct */
> u_long ifi_mtu; /* maximum transmission unit */
> u_long ifi_metric; /* routing metric (external only) */
> u_long ifi_baudrate; /* linespeed */
>=20
> So any already compiled executables that use the if_data structure would
> be looking for ifi_mtu/ifi_metric/ifi_baudrate in the wrong place after
> this change. Are you absolutely sure this is not breaking ABI?
ifi_mtu, etc remain in the same location because the two new variables
fill in the hidden padding required to align ifi_mtu. I've verified
that old and new ifconfigs work with old and new kernels. The change
will allow 4.11 ifconfigs to work with 6.x if we add fields to struct
if_data (fairly probable).
-- Brooks
--=20
Any statement of the form "X is the one, true Y" is FALSE.
PGP fingerprint 655D 519C 26A7 82E7 2529 9BF0 5D8E 8BE9 F238 1AD4
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