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mctp: Add SIOCMCTP{ALLOC,DROP}TAG ioctls for tag control

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This change adds a couple of new ioctls for mctp sockets:
SIOCMCTPALLOCTAG and SIOCMCTPDROPTAG.  These ioctls provide facilities
for explicit allocation / release of tags, overriding the automatic
allocate-on-send/release-on-reply and timeout behaviours. This allows
userspace more control over messages that may not fit a simple
request/response model.

In order to indicate a pre-allocated tag to the sendmsg() syscall, we
introduce a new flag to the struct sockaddr_mctp.smctp_tag value:
MCTP_TAG_PREALLOC.

Additional changes from Jeremy Kerr <jk@codeconstruct.com.au>.

Contains a fix that was:
Reported-by: kernel test robot <lkp@intel.com>

Signed-off-by: Matt Johnston <matt@codeconstruct.com.au>
Signed-off-by: Jeremy Kerr <jk@codeconstruct.com.au>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Matt Johnston 2022-02-09 12:05:57 +08:00 • committed by David S. Miller
parent 0de55a7d11
commit 63ed1aab3d
6 changed files with 329 additions and 56 deletions
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18
include/uapi/linux/mctp.h
View file

@ -44,7 +44,25 @@ struct sockaddr_mctp_ext {
#define MCTP_TAG_MASK 0x07
#define MCTP_TAG_OWNER 0x08
#define MCTP_TAG_PREALLOC 0x10
#define MCTP_OPT_ADDR_EXT 1
#define SIOCMCTPALLOCTAG (SIOCPROTOPRIVATE + 0)
#define SIOCMCTPDROPTAG (SIOCPROTOPRIVATE + 1)
struct mctp_ioc_tag_ctl {
mctp_eid_t peer_addr;
/* For SIOCMCTPALLOCTAG: must be passed as zero, kernel will
* populate with the allocated tag value. Returned tag value will
* always have TO and PREALLOC set.
*
* For SIOCMCTPDROPTAG: userspace provides tag value to drop, from
* a prior SIOCMCTPALLOCTAG call (and so must have TO and PREALLOC set).
*/
__u8 tag;
__u16 flags;
};
#endif /* __UAPI_MCTP_H */