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| author | Alexander V. Chernikov <melifaro@FreeBSD.org> | 2022-11-30 12:15:23 +0000 |
|---|---|---|
| committer | Alexander V. Chernikov <melifaro@FreeBSD.org> | 2023-01-23 22:04:03 +0000 |
| commit | a6b537f6b9459dbc0f5f2f60d973f025c6e63782 (patch) | |
| tree | 1a4012a2895dcfb3ab81c5758dc008ddd8d884b5 /sys/netlink/netlink_message_writer.h | |
| parent | 02b958b19535828d8f19bf3601ae88ecf4503d33 (diff) | |
| download | src-a6b537f6b9459dbc0f5f2f60d973f025c6e63782.tar.gz src-a6b537f6b9459dbc0f5f2f60d973f025c6e63782.zip | |
netlink: suppress sending NLMSG_ERROR if NLMSG_DONE is already sent
Netlink has a confirmation/error reporting mechanism for the sent
messages. Kernel explicitly acks each messages if requested (NLM_F_ACK)
or if message processing results in an error.
Similarly, for multipart messages - typically dumps, where each message
represents a single object like an interface or a route - another
message, NLMSG_DONE is used to indicate the end of dump and the
resulting status.
As a result, successfull dump ends with both NLMSG_DONE and NLMSG_ERROR
messages.
RFC 3549 does not say anything specific about such case.
Linux adopted an optimisation which suppresses NLMSG_ERROR message
when NLMSG_DONE is already sent. Certain libraries/applications like
libnl depends on such behavior.
Suppress sending NLMSG_ERROR if NLMSG_DONE is already sent, by
setting newly-added 'suppress_ack' flag in the writer and checking
this flag when generating ack.
This change restores libnl compatibility.
Before:
```
~ nl-link-list
Error: Unable to allocate link cache: Message sequence number mismatch
````
After:
```
~ nl-link-list
vtnet0 ether 52:54:00:14:e3:19 <broadcast,multicast,up,running>
lo0 ieee1394 <loopback,multicast,up,running>
```
Reviewed by: bapt,pauamma
Tested by: bapt
Differential Revision: https://reviews.freebsd.org/D37565
(cherry picked from commit f4d3aa74908496f1f5815caca94ebd86944b17cb)
Diffstat (limited to 'sys/netlink/netlink_message_writer.h')
| -rw-r--r-- | sys/netlink/netlink_message_writer.h | 1 |
1 files changed, 1 insertions, 0 deletions
diff --git a/sys/netlink/netlink_message_writer.h b/sys/netlink/netlink_message_writer.h index 424983282e59..99f50fb94213 100644 --- a/sys/netlink/netlink_message_writer.h +++ b/sys/netlink/netlink_message_writer.h @@ -55,6 +55,7 @@ struct nl_writer { uint8_t writer_target; /* NS_WRITER_TARGET_* */ bool ignore_limit; /* If true, ignores RCVBUF limit */ bool enomem; /* True if ENOMEM occured */ + bool suppress_ack; /* If true, don't send NLMSG_ERR */ }; #define NS_WRITER_TARGET_SOCKET 0 #define NS_WRITER_TARGET_GROUP 1 |