[Libguestfs] [libnbd PATCH v4 2/4] generator: Finish parsing structured header in states-reply.c
Eric Blake
eblake at redhat.com
Fri Jun 9 02:17:36 UTC 2023
Splitting the parse of a 20-byte structured reply header across two
source files (16 bytes overlapping with simple replies in
states-reply.c, the remaining 4 bytes in states-reply-structured.c) is
confusing. The upcoming addition of extended headers will reuse the
payload parsing portion of structured replies, but will parse its
32-byte header completely in states-reply.c. So it is better to have
a single file in charge of parsing all three header sizes (once the
third type is introduced), where we then farm out to the payload
parsers.
To do that, rename REPLY.CHECK_SIMPLE_OR_STRUCTURED_REPLY to
REPLY.CHECK_REPLY_MAGIC and have it pick up the setup from
REPLY.STRUCTURED_REPLY.START, rename REPLY
REPLY.STRUCTURED_REPLY.RECV_REMAINING to
REPLY.RECV_STRUCTURED_REMAINING across files, and merge
REPLY.STRUCTURED_REPLY.CHECK into what would otherwise be the
now-empty REPLY.STRUCTURED_REPLY.START.
Signed-off-by: Eric Blake <eblake at redhat.com>
---
generator/state_machine.ml | 29 ++++++++-----------
generator/states-reply.c | 43 ++++++++++++++++++++++-------
generator/states-reply-structured.c | 26 -----------------
3 files changed, 44 insertions(+), 54 deletions(-)
diff --git a/generator/state_machine.ml b/generator/state_machine.ml
index 126159b9..b5485aec 100644
--- a/generator/state_machine.ml
+++ b/generator/state_machine.ml
@@ -769,8 +769,15 @@ and
State {
default_state with
- name = "CHECK_SIMPLE_OR_STRUCTURED_REPLY";
- comment = "Check if the reply is a simple or structured reply";
+ name = "CHECK_REPLY_MAGIC";
+ comment = "Check if the reply has expected magic";
+ external_events = [];
+ };
+
+ State {
+ default_state with
+ name = "RECV_STRUCTURED_REMAINING";
+ comment = "Receiving the remaining part of a structured reply header";
external_events = [];
};
@@ -804,28 +811,14 @@ and
};
]
-(* Receiving a structured reply from the server.
+(* Receiving a structured reply payload from the server.
* Implementation: generator/states-reply-structured.c
*)
and structured_reply_state_machine = [
State {
default_state with
name = "START";
- comment = "Prepare to receive the remaining part of a structured reply";
- external_events = [];
- };
-
- State {
- default_state with
- name = "RECV_REMAINING";
- comment = "Receiving the remaining part of a structured reply";
- external_events = [];
- };
-
- State {
- default_state with
- name = "CHECK";
- comment = "Parse a structured reply from the server";
+ comment = "Start parsing a structured reply payload from the server";
external_events = [];
};
diff --git a/generator/states-reply.c b/generator/states-reply.c
index 2c77658b..87f17bae 100644
--- a/generator/states-reply.c
+++ b/generator/states-reply.c
@@ -64,11 +64,11 @@ REPLY.START:
ssize_t r;
/* We read all replies initially as if they are simple replies, but
- * check the magic in CHECK_SIMPLE_OR_STRUCTURED_REPLY below. This
- * works because the structured_reply header is larger, and because
- * the last member of a simple reply, cookie, is coincident between
- * the two structs (an intentional design decision in the NBD spec
- * when structured replies were added).
+ * check the magic in CHECK_REPLY_MAGIC below. This works because
+ * the structured_reply header is larger, and because the last
+ * member of a simple reply, cookie, is coincident between the two
+ * structs (an intentional design decision in the NBD spec when
+ * structured replies were added).
*/
STATIC_ASSERT (offsetof (struct nbd_handle, sbuf.simple_reply.cookie) ==
offsetof (struct nbd_handle, sbuf.sr.structured_reply.cookie),
@@ -113,11 +113,11 @@ REPLY.RECV_REPLY:
switch (recv_into_rbuf (h)) {
case -1: SET_NEXT_STATE (%.DEAD); return 0;
case 1: SET_NEXT_STATE (%.READY); return 0;
- case 0: SET_NEXT_STATE (%CHECK_SIMPLE_OR_STRUCTURED_REPLY);
+ case 0: SET_NEXT_STATE (%CHECK_REPLY_MAGIC);
}
return 0;
- REPLY.CHECK_SIMPLE_OR_STRUCTURED_REPLY:
+ REPLY.CHECK_REPLY_MAGIC:
struct command *cmd;
uint32_t magic;
uint64_t cookie;
@@ -127,7 +127,18 @@ REPLY.CHECK_SIMPLE_OR_STRUCTURED_REPLY:
SET_NEXT_STATE (%SIMPLE_REPLY.START);
}
else if (magic == NBD_STRUCTURED_REPLY_MAGIC) {
- SET_NEXT_STATE (%STRUCTURED_REPLY.START);
+ /* We've only read the bytes that fill simple_reply. The
+ * structured_reply is longer, so prepare to read the remaining
+ * bytes. We depend on the memory aliasing in union sbuf to
+ * overlay the two reply types.
+ */
+ STATIC_ASSERT (sizeof h->sbuf.simple_reply ==
+ offsetof (struct nbd_structured_reply, length),
+ simple_structured_overlap);
+ assert (h->rbuf == (char *)&h->sbuf + sizeof h->sbuf.simple_reply);
+ h->rlen = sizeof h->sbuf.sr.structured_reply;
+ h->rlen -= sizeof h->sbuf.simple_reply;
+ SET_NEXT_STATE (%RECV_STRUCTURED_REMAINING);
}
else {
/* We've probably lost synchronization. */
@@ -141,8 +152,9 @@ REPLY.CHECK_SIMPLE_OR_STRUCTURED_REPLY:
return 0;
}
- /* NB: This works for both simple and structured replies because the
- * handle (our cookie) is stored at the same offset. See the
+ /* NB: This works for both simple and structured replies, even
+ * though we haven't finished reading the structured header yet,
+ * because the cookie is stored at the same offset. See the
* STATIC_ASSERT above in state REPLY.START that confirmed this.
*/
h->chunks_received++;
@@ -157,6 +169,17 @@ REPLY.CHECK_SIMPLE_OR_STRUCTURED_REPLY:
h->reply_cmd = cmd;
return 0;
+ REPLY.RECV_STRUCTURED_REMAINING:
+ switch (recv_into_rbuf (h)) {
+ case -1: SET_NEXT_STATE (%.DEAD); return 0;
+ case 1:
+ save_reply_state (h);
+ SET_NEXT_STATE (%.READY);
+ return 0;
+ case 0: SET_NEXT_STATE (%STRUCTURED_REPLY.START);
+ }
+ return 0;
+
REPLY.FINISH_COMMAND:
struct command *prev_cmd, *cmd;
uint64_t cookie;
diff --git a/generator/states-reply-structured.c b/generator/states-reply-structured.c
index 205a236d..3a7a03fd 100644
--- a/generator/states-reply-structured.c
+++ b/generator/states-reply-structured.c
@@ -46,32 +46,6 @@ structured_reply_in_bounds (uint64_t offset, uint32_t length,
STATE_MACHINE {
REPLY.STRUCTURED_REPLY.START:
- /* We've only read the bytes that fill simple_reply. The
- * structured_reply is longer, so read the remaining part. We
- * depend on the memory aliasing in union sbuf to overlay the two
- * reply types.
- */
- STATIC_ASSERT (sizeof h->sbuf.simple_reply ==
- offsetof (struct nbd_structured_reply, length),
- simple_structured_overlap);
- assert (h->rbuf == (char *)&h->sbuf + sizeof h->sbuf.simple_reply);
- h->rlen = sizeof h->sbuf.sr.structured_reply;
- h->rlen -= sizeof h->sbuf.simple_reply;
- SET_NEXT_STATE (%RECV_REMAINING);
- return 0;
-
- REPLY.STRUCTURED_REPLY.RECV_REMAINING:
- switch (recv_into_rbuf (h)) {
- case -1: SET_NEXT_STATE (%.DEAD); return 0;
- case 1:
- save_reply_state (h);
- SET_NEXT_STATE (%.READY);
- return 0;
- case 0: SET_NEXT_STATE (%CHECK);
- }
- return 0;
-
- REPLY.STRUCTURED_REPLY.CHECK:
struct command *cmd = h->reply_cmd;
uint16_t flags, type;
uint32_t length;
--
2.40.1
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