diff mbox series

[net] net/smc: avoid data corruption caused by decline

Message ID 1699329376-17596-1-git-send-email-alibuda@linux.alibaba.com (mailing list archive)
State Superseded
Delegated to: Netdev Maintainers
Headers show
Series [net] net/smc: avoid data corruption caused by decline | expand

Checks

Context Check Description
netdev/series_format success Single patches do not need cover letters
netdev/tree_selection success Clearly marked for net
netdev/fixes_present fail Series targets non-next tree, but doesn't contain any Fixes tags
netdev/header_inline success No static functions without inline keyword in header files
netdev/build_32bit success Errors and warnings before: 1312 this patch: 1312
netdev/cc_maintainers warning 4 maintainers not CCed: tonylu@linux.alibaba.com pabeni@redhat.com edumazet@google.com guwen@linux.alibaba.com
netdev/build_clang success Errors and warnings before: 1340 this patch: 1340
netdev/verify_signedoff success Signed-off-by tag matches author and committer
netdev/deprecated_api success None detected
netdev/check_selftest success No net selftest shell script
netdev/verify_fixes success No Fixes tag
netdev/build_allmodconfig_warn success Errors and warnings before: 1340 this patch: 1340
netdev/checkpatch success total: 0 errors, 0 warnings, 0 checks, 8 lines checked
netdev/build_clang_rust success No Rust files in patch. Skipping build
netdev/kdoc success Errors and warnings before: 0 this patch: 0
netdev/source_inline success Was 0 now: 0

Commit Message

D. Wythe Nov. 7, 2023, 3:56 a.m. UTC 
From: "D. Wythe" <alibuda@linux.alibaba.com>

We found a data corruption issue during testing of SMC-R on Redis
applications.

The benchmark has a low probability of reporting a strange error as
shown below.

"Error: Protocol error, got "\xe2" as reply type byte"

Finally, we found that the retrieved error data was as follows:

0xE2 0xD4 0xC3 0xD9 0x04 0x00 0x2C 0x20 0xA6 0x56 0x00 0x16 0x3E 0x0C
0xCB 0x04 0x02 0x01 0x00 0x00 0x20 0x00 0x00 0x00 0x00 0x00 0x00 0x00
0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0xE2

It is quite obvious that this is a SMC DECLINE message, which means that
the applications received SMC protocol message.
We found that this was caused by the following situations:

client			server
	   proposal
	------------->
	   accept
	<-------------
	   confirm
	------------->
wait confirm

	 failed llc confirm
	    x------
(after 2s)timeout
			wait rsp

wait decline

(after 1s) timeout
			(after 2s) timeout
	    decline
	-------------->
	    decline
	<--------------

As a result, a decline message was sent in the implementation, and this
message was read from TCP by the already-fallback connection.

This patch double the client timeout as 2x of the server value,
With this simple change, the Decline messages should never cross or
collide (during Confirm link timeout).

This issue requires an immediate solution, since the protocol updates
involve a more long-term solution.

Signed-off-by: D. Wythe <alibuda@linux.alibaba.com>
---
 net/smc/af_smc.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Comments

Jakub Kicinski Nov. 8, 2023, 2:38 a.m. UTC | #1 
On Tue,  7 Nov 2023 11:56:16 +0800 D. Wythe wrote:
> This issue requires an immediate solution, since the protocol updates
> involve a more long-term solution.

Please provide an appropriate Fixes tag.
D. Wythe Nov. 8, 2023, 9:42 a.m. UTC | #2 
On 11/8/23 10:38 AM, Jakub Kicinski wrote:
> On Tue,  7 Nov 2023 11:56:16 +0800 D. Wythe wrote:
>> This issue requires an immediate solution, since the protocol updates
>> involve a more long-term solution.
> Please provide an appropriate Fixes tag.

Thanks for reminder.

D. Wythe
diff mbox series

Patch

diff --git a/net/smc/af_smc.c b/net/smc/af_smc.c
index abd2667..5b91f55 100644
--- a/net/smc/af_smc.c
+++ b/net/smc/af_smc.c
@@ -599,7 +599,7 @@  static int smcr_clnt_conf_first_link(struct smc_sock *smc)
 	int rc;
 
 	/* receive CONFIRM LINK request from server over RoCE fabric */
-	qentry = smc_llc_wait(link->lgr, NULL, SMC_LLC_WAIT_TIME,
+	qentry = smc_llc_wait(link->lgr, NULL, 2 * SMC_LLC_WAIT_TIME,
 			      SMC_LLC_CONFIRM_LINK);
 	if (!qentry) {
 		struct smc_clc_msg_decline dclc;