BUG/MEDIUM: stktable: fix sc_*(<ctr>) BUG_ON() regression with ctx > 9

As reported in GH #2958, commit 6c9b315 caused a regression with sc_*
fetches and tracked counter id > 9.

As such, the below configuration would cause a BUG_ON() to be triggered:

  global
    log stdout format raw local0
    tune.stick-counters 11

  defaults
    log global
    mode http

  frontend www
    bind *:8080

    acl track_me bool(true)
    http-request set-var(txn.track_var) str("a")
    http-request track-sc10 var(txn.track_var) table rate_table if track_me
    http-request set-var(txn.track_var_rate) sc_gpc_rate(0,10,rate_table)
    http-request return status 200

  backend rate_table
      stick-table type string size 1k expire 5m store gpc_rate(1,1m)

While in 6c9b315 the src_fetch logic was removed from
smp_fetch_sc_stkctr(), num > 9 is indeed not expected anymore as
original num value. But what we didn't consider is that num is effectively
re-assigned for generic sc_* variant.

Thus the BUG_ON() is misplaced as it should only be evaluated for
non-generic fetches. It explains why it triggers with valid configurations

Thanks to GH user @tkjaer for his detailed report and bug analysis

No backport needed, this bug is specific to 3.2.

diff --git a/src/stick_table.c b/src/stick_table.c
index 9e7249fdccd4ed1328b832d52704a46e59dffbcf..31692082fd7b00aae4b074e95813eabb5fc670ac 100644 (file)
--- a/src/stick_table.c
+++ b/src/stick_table.c
@@ -3236,8 +3236,8 @@ smp_fetch_sc_stkctr(struct session *sess, struct stream *strm, const struct arg
                /* sc_* variant, args[0] = ctr# (mandatory) */
                num = args[arg++].data.sint;
        }
-
-       BUG_ON(num > 9, "unexpected value");
+       else
+               BUG_ON(num > 9, "unexpected value");
 
        /* Here, <num> contains the counter number from 0 to 9 for
         * the sc[0-9]_ form, or even higher using sc_(num) if needed.