[dm-devel] [PATCH v2 29/48] multipathd: uxlsnr: merge uxsock_trigger() into state machine
mwilck at suse.com
mwilck at suse.com
Thu Nov 18 22:58:21 UTC 2021
From: Martin Wilck <mwilck at suse.com>
This patch sets up the bulk of the state machine. client_state_machine()
is called in a loop, proceeding from state to state until it needs
to poll for input or wait for a lock, in which case it returns
STM_BREAK.
While doing this, switch to negative error codes for the functions
in uxlsnr.c (e.g. parse_cmd()). Positive return codes are reserved
for the cli_handler functions themselves. This way we can clearly
distinguish the error source, and avoid confusion and misleading
error messages. No cli_handler returns negative values.
Note: with this patch applied, clients may hang and time out if
the handler fails to acquire the vecs lock. This will be fixed in the
follow-up patch "multipathd: uxlsnr: add idle notification".
Signed-off-by: Martin Wilck <mwilck at suse.com>
---
multipathd/uxlsnr.c | 160 ++++++++++++++++++++++++--------------------
1 file changed, 89 insertions(+), 71 deletions(-)
diff --git a/multipathd/uxlsnr.c b/multipathd/uxlsnr.c
index ff9604f..87134d5 100644
--- a/multipathd/uxlsnr.c
+++ b/multipathd/uxlsnr.c
@@ -299,22 +299,13 @@ static int parse_cmd(struct client *c)
r = get_cmdvec(c->cmd, &c->cmdvec);
- if (r) {
- genhelp_handler(c->cmd, r, &c->reply);
- if (get_strbuf_len(&c->reply) == 0)
- return EINVAL;
- return 0;
- }
+ if (r)
+ return -r;
c->handler = find_handler_for_cmdvec(c->cmdvec);
- if (!c->handler || !c->handler->fn) {
- genhelp_handler(c->cmd, EINVAL, &c->reply);
- if (get_strbuf_len(&c->reply) == 0)
- r = EINVAL;
- else
- r = 0;
- }
+ if (!c->handler || !c->handler->fn)
+ return -EINVAL;
return r;
}
@@ -325,7 +316,7 @@ static int execute_handler(struct client *c, struct vectors *vecs, int timeout)
struct timespec tmo;
if (!c->handler)
- return EINVAL;
+ return -EINVAL;
if (clock_gettime(CLOCK_REALTIME, &tmo) == 0) {
tmo.tv_sec += timeout;
@@ -355,50 +346,30 @@ static int execute_handler(struct client *c, struct vectors *vecs, int timeout)
return r;
}
-static int uxsock_trigger(struct client *c, void *trigger_data)
+void default_reply(struct client *c, int r)
{
- struct vectors * vecs;
- int r = 1;
-
- vecs = (struct vectors *)trigger_data;
-
- r = parse_cmd(c);
-
- if (r == 0 && c->cmdvec && VECTOR_SIZE(c->cmdvec) > 0) {
- struct key *kw = VECTOR_SLOT(c->cmdvec, 0);
-
- if (!c->is_root && kw->code != LIST)
- r = EPERM;
- }
-
- if (r == 0 && c->handler)
- r = execute_handler(c, vecs, uxsock_timeout / 1000);
-
- if (c->cmdvec) {
- free_keys(c->cmdvec);
- c->cmdvec = NULL;
- }
-
- if (r > 0) {
- switch(r) {
- case ETIMEDOUT:
- append_strbuf_str(&c->reply, "timeout\n");
- break;
- case EPERM:
- append_strbuf_str(&c->reply,
- "permission deny: need to be root\n");
- break;
- default:
- append_strbuf_str(&c->reply, "fail\n");
- break;
- }
- }
- else if (!r && get_strbuf_len(&c->reply) == 0) {
+ switch(r) {
+ case -EINVAL:
+ case -ESRCH:
+ case -ENOMEM:
+ /* return codes from get_cmdvec() */
+ genhelp_handler(c->cmd, -r, &c->reply);
+ break;
+ case -EPERM:
+ append_strbuf_str(&c->reply,
+ "permission deny: need to be root\n");
+ break;
+ case -ETIMEDOUT:
+ append_strbuf_str(&c->reply, "timeout\n");
+ break;
+ case 0:
append_strbuf_str(&c->reply, "ok\n");
- r = 0;
+ break;
+ default:
+ /* cli_handler functions return 1 on unspecified error */
+ append_strbuf_str(&c->reply, "fail\n");
+ break;
}
- /* else if (r < 0) leave *reply alone */
- return r;
}
static void set_client_state(struct client *c, int state)
@@ -409,6 +380,7 @@ static void set_client_state(struct client *c, int state)
reset_strbuf(&c->reply);
memset(c->cmd, '\0', sizeof(c->cmd));
c->expires = ts_zero;
+ c->error = 0;
/* fallthrough */
case CLT_SEND:
/* reuse these fields for next data transfer */
@@ -420,11 +392,20 @@ static void set_client_state(struct client *c, int state)
c->state = state;
}
-static void handle_client(struct client *c, void *trigger_data)
+enum {
+ STM_CONT,
+ STM_BREAK,
+};
+
+static int client_state_machine(struct client *c, struct vectors *vecs)
{
ssize_t n;
+ const char *buf;
- switch (c->state) {
+ condlog(4, "%s: cli[%d] state=%d cmd=\"%s\" repl \"%s\"", __func__,
+ c->fd, c->state, c->cmd, get_strbuf_str(&c->reply));
+
+ switch (c->state) {
case CLT_RECV:
if (c->cmd_len == 0) {
/*
@@ -449,31 +430,59 @@ static void handle_client(struct client *c, void *trigger_data)
condlog(4, "%s: cli[%d]: connected", __func__, c->fd);
}
/* poll for data */
- return;
+ return STM_BREAK;
} else if (c->len < c->cmd_len) {
n = recv(c->fd, c->cmd + c->len, c->cmd_len - c->len, 0);
if (n <= 0 && errno != EINTR && errno != EAGAIN) {
condlog(1, "%s: cli[%d]: error in recv: %m",
__func__, c->fd);
c->error = -ECONNRESET;
- return;
+ return STM_BREAK;
}
c->len += n;
if (c->len < c->cmd_len)
/* continue polling */
- return;
- set_client_state(c, CLT_PARSE);
+ return STM_BREAK;
}
- break;
- default:
- break;
- }
+ condlog(4, "cli[%d]: Got request [%s]", c->fd, c->cmd);
+ set_client_state(c, CLT_PARSE);
+ return STM_CONT;
- condlog(4, "cli[%d]: Got request [%s]", c->fd, c->cmd);
- uxsock_trigger(c, trigger_data);
+ case CLT_PARSE:
+ c->error = parse_cmd(c);
+ if (!c->error) {
+ /* Permission check */
+ struct key *kw = VECTOR_SLOT(c->cmdvec, 0);
- if (get_strbuf_len(&c->reply) > 0) {
- const char *buf = get_strbuf_str(&c->reply);
+ if (!c->is_root && kw->code != LIST) {
+ c->error = -EPERM;
+ condlog(0, "%s: cli[%d]: unauthorized cmd \"%s\"",
+ __func__, c->fd, c->cmd);
+ }
+ }
+ if (c->error)
+ set_client_state(c, CLT_SEND);
+ else
+ set_client_state(c, CLT_WORK);
+ return STM_CONT;
+
+ case CLT_WAIT_LOCK:
+ /* tbd */
+ set_client_state(c, CLT_WORK);
+ return STM_CONT;
+
+ case CLT_WORK:
+ c->error = execute_handler(c, vecs, uxsock_timeout / 1000);
+ free_keys(c->cmdvec);
+ c->cmdvec = NULL;
+ set_client_state(c, CLT_SEND);
+ return STM_CONT;
+
+ case CLT_SEND:
+ if (get_strbuf_len(&c->reply) == 0)
+ default_reply(c, c->error);
+
+ buf = get_strbuf_str(&c->reply);
if (send_packet(c->fd, buf) != 0)
dead_client(c);
@@ -481,9 +490,18 @@ static void handle_client(struct client *c, void *trigger_data)
condlog(4, "cli[%d]: Reply [%zu bytes]", c->fd,
get_strbuf_len(&c->reply) + 1);
reset_strbuf(&c->reply);
- }
- set_client_state(c, CLT_RECV);
+ set_client_state(c, CLT_RECV);
+ return STM_BREAK;
+
+ default:
+ return STM_BREAK;
+ }
+}
+
+static void handle_client(struct client *c, struct vectors *vecs)
+{
+ while (client_state_machine(c, vecs) == STM_CONT);
}
/*
--
2.33.1
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