Date: Wed, 3 Oct 2018 00:40:27 +0000 From: Rick Macklem <rmacklem@uoguelph.ca> To: "freebsd-current@FreeBSD.org" <freebsd-current@FreeBSD.org> Cc: Josh Paetzel <josh@tcbug.org> Subject: which way to update export_args structure? Message-ID: <YTOPR0101MB182021549F8CF8277477A4C5DDE90@YTOPR0101MB1820.CANPRD01.PROD.OUTLOOK.COM>
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Hi,
I am working on updating "struct export_args" to fix/add a few things.
One of these is that "ex_flags" is an int, but the flags are defined in mou=
nt.h
as MNT_xx bits that now exceed 32bits (mnt_flag is now uint64_t).
For now, this doesn't break anything, since the flags used by ex_flags are
all defined in the low order 32bits but...it seems like this should be addr=
essed
by a new version of "struct export_args".
I have two versions of the updated structure:
A)
struct export_args {
uint64_t ex_flags; /* export related flags */
uid_t ex_root; /* mapping for root uid */
struct xucred ex_anon; /* mapping for anonymous user */
struct sockaddr *ex_addr; /* net address to which exported */
u_char ex_addrlen; /* and the net address length */
struct sockaddr *ex_mask; /* mask of valid bits in saddr */
u_char ex_masklen; /* and the smask length */
char *ex_indexfile; /* index file for WebNFS URLs */
int ex_numsecflavors; /* security flavor count */
int ex_secflavors[MAXSECFLAVORS]; /* list of security flavors */
int32_t ex_fsid; /* mnt_stat.f_fsid.val[0] if */
/* MNT_EXPORTFSID set in ex_flags64 */
gid_t *ex_suppgroups; /* Supplemental groups if */
/* ex_anon.cr_ngroups > XU_NGROUPS */
};
B)
struct export_args {
int ex_flags; /* export related flags */
uid_t ex_root; /* mapping for root uid */
struct xucred ex_anon; /* mapping for anonymous user */
struct sockaddr *ex_addr; /* net address to which exported */
u_char ex_addrlen; /* and the net address length */
struct sockaddr *ex_mask; /* mask of valid bits in saddr */
u_char ex_masklen; /* and the smask length */
char *ex_indexfile; /* index file for WebNFS URLs */
int ex_numsecflavors; /* security flavor count */
int ex_secflavors[MAXSECFLAVORS]; /* list of security flavors */
uint64_t ex_flagshighbits; /* High order bits of mnt_flag */
int32_t ex_fsid; /* mnt_stat.f_fsid.val[0] if */
/* MNT_EXPORTFSID set in ex_flags64 */
gid_t *ex_suppgroups; /* Supplemental groups if */
/* ex_anon.cr_ngroups > XU_NGROUPS */
};
A) does the obvious thing. Unfortunately, this changes the vfs KABI
(specifically the function vfs_oexport_conv()) such that a file system
module compiled with an unpatched mount.h could crash a patched system.
As such, I think it couldn't be MFC'd and would be stuck in head/current
until FreeBSD13 (or FreeBSD14 if 13 gets skipped over;-).
B) doesn't change any fields, but adds a second ex_flagshighbits for the hi=
gh
order bit. Since it only adds fields where none of those bits are used afte=
r
the exports are processed by vfs_export() and, as such, will not break
the VFS KABI, since vfs_domount_update() differentiates which version
of export_args is being used.
As such, I believe this version can be MFC'd. However, it does seem confusi=
ng
to have the two ex_flags fields for the low and high 32bits.
So, which do you think it preferable? rick
ps: Josh Paetzel has volunteered to do the mountd.c changes and I have a ke=
rne
patch that I'll put up on phabricator once Josh has been able to test=
it.
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