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authorAlexander Aring <aahringo@redhat.com>2021-05-21 22:08:46 +0300
committerDavid Teigland <teigland@redhat.com>2021-05-25 17:22:20 +0300
commit489d8e559c6596eb08e16447d9830bc39afbe54e (patch)
treec6d9172d5f8db2488c8fe19fb51e59b34e02dcdc /fs/dlm/dlm_internal.h
parent8e2e40860c7f67c0b19b13d92cfea03a19232ce2 (diff)
downloadlinux-489d8e559c6596eb08e16447d9830bc39afbe54e.tar.xz
fs: dlm: add reliable connection if reconnect
This patch introduce to make a tcp lowcomms connection reliable even if reconnects occurs. This is done by an application layer re-transmission handling and sequence numbers in dlm protocols. There are three new dlm commands: DLM_OPTS: This will encapsulate an existing dlm message (and rcom message if they don't have an own application side re-transmission handling). As optional handling additional tlv's (type length fields) can be appended. This can be for example a sequence number field. However because in DLM_OPTS the lockspace field is unused and a sequence number is a mandatory field it isn't made as a tlv and we put the sequence number inside the lockspace id. The possibility to add optional options are still there for future purposes. DLM_ACK: Just a dlm header to acknowledge the receive of a DLM_OPTS message to it's sender. DLM_FIN: This provides a 4 way handshake for connection termination inclusive support for half-closed connections. It's provided on application layer because SCTP doesn't support half-closed sockets, the shutdown() call can interrupted by e.g. TCP resets itself and a hard logic to implement it because the othercon paradigm in lowcomms. The 4-way termination handshake also solve problems to synchronize peer EOF arrival and that the cluster manager removes the peer in the node membership handling of DLM. In some cases messages can be still transmitted in this time and we need to wait for the node membership event. To provide a reliable connection the node will retransmit all unacknowledges message to it's peer on reconnect. The receiver will then filtering out the next received message and drop all messages which are duplicates. As RCOM_STATUS and RCOM_NAMES messages are the first messages which are exchanged and they have they own re-transmission handling, there exists logic that these messages must be first. If these messages arrives we store the dlm version field. This handling is on DLM 3.1 and after this patch 3.2 the same. A backwards compatibility handling has been added which seems to work on tests without tcpkill, however it's not recommended to use DLM 3.1 and 3.2 at the same time, because DLM 3.2 tries to fix long term bugs in the DLM protocol. Signed-off-by: Alexander Aring <aahringo@redhat.com> Signed-off-by: David Teigland <teigland@redhat.com>
Diffstat (limited to 'fs/dlm/dlm_internal.h')
-rw-r--r--fs/dlm/dlm_internal.h30
1 files changed, 28 insertions, 2 deletions
diff --git a/fs/dlm/dlm_internal.h b/fs/dlm/dlm_internal.h
index 8f5980909d80..40917c878370 100644
--- a/fs/dlm/dlm_internal.h
+++ b/fs/dlm/dlm_internal.h
@@ -371,18 +371,26 @@ static inline int rsb_flag(struct dlm_rsb *r, enum rsb_flags flag)
/* dlm_header is first element of all structs sent between nodes */
#define DLM_HEADER_MAJOR 0x00030000
-#define DLM_HEADER_MINOR 0x00000001
+#define DLM_HEADER_MINOR 0x00000002
+
+#define DLM_VERSION_3_1 0x00030001
+#define DLM_VERSION_3_2 0x00030002
#define DLM_HEADER_SLOTS 0x00000001
#define DLM_MSG 1
#define DLM_RCOM 2
+#define DLM_OPTS 3
+#define DLM_ACK 4
+#define DLM_FIN 5
struct dlm_header {
uint32_t h_version;
union {
/* for DLM_MSG and DLM_RCOM */
uint32_t h_lockspace;
+ /* for DLM_ACK and DLM_OPTS */
+ uint32_t h_seq;
} u;
uint32_t h_nodeid; /* nodeid of sender */
uint16_t h_length;
@@ -390,7 +398,6 @@ struct dlm_header {
uint8_t h_pad;
};
-
#define DLM_MSG_REQUEST 1
#define DLM_MSG_CONVERT 2
#define DLM_MSG_UNLOCK 3
@@ -458,10 +465,29 @@ struct dlm_rcom {
char rc_buf[];
};
+struct dlm_opt_header {
+ uint16_t t_type;
+ uint16_t t_length;
+ uint32_t o_pad;
+ /* need to be 8 byte aligned */
+ char t_value[];
+};
+
+/* encapsulation header */
+struct dlm_opts {
+ struct dlm_header o_header;
+ uint8_t o_nextcmd;
+ uint8_t o_pad;
+ uint16_t o_optlen;
+ uint32_t o_pad2;
+ char o_opts[];
+};
+
union dlm_packet {
struct dlm_header header; /* common to other two */
struct dlm_message message;
struct dlm_rcom rcom;
+ struct dlm_opts opts;
};
#define DLM_RSF_NEED_SLOTS 0x00000001