MINOR: quic: allow BBR testing without pacing

Pacing is activated per bind line via an optional boolean argument of
quic-cc-algo keyword. Contrary to the default usage, pacing is
automatically activated when BBR is chosen. This is because this
algorithm is expected to run on top of pacing, else its behavior is
undefined.

Previously, pacing argument was thus ignored when BBR was selected.
Change this to support explicit deactivation of pacing with it. This
could be useful to test BBR without pacing when debugging some issues.

This should be backported up to 3.1, after a period of observation.

diff --git a/doc/configuration.txt b/doc/configuration.txt
index da9d8b540dc018827827a92496da4e4435e57abe..0ebfd32919aac6d1a06bbd0b074007d68b80afe8 100644 (file)
--- a/doc/configuration.txt
+++ b/doc/configuration.txt
@@ -17297,9 +17297,10 @@ quic-cc-algo { cubic | newreno | bbr | nocc }[(<args,...>)]
   The purpose of pacing is to smooth emission of data to reduce network losses.
   In most scenario, it can significantly improve network throughput by avoiding
   retransmissions. Pacing support is still experimental, as such it requires
-  "expose-experimental-directives". The BBR congestion control algorithm
-  depends on the pacing support which is in this case implicitly enabled by
-  choosing the "bbr" algorithm. Note that haproxy's BBR implementation is still
+  "expose-experimental-directives". Selecting BBR congestion algorithm will
+  implicitly activate pacing as it relies on it to work as expected. Explicitly
+  disabling pacing in conjunction with BBR may cause slowdowns or high loss
+  rates during transfers. Also note that haproxy's BBR implementation is also
   considered as experimental and cannot be enabled without
   "expose-experimental-directives".
 
@@ -17311,8 +17312,7 @@ quic-cc-algo { cubic | newreno | bbr | nocc }[(<args,...>)]
     4g. By default "tune.quic.frontend.default-max-window-size" value is used.
   - pacing activation. By default, it is set to 0, which means pacing is not
     used. To activate it, specify a positive value. Burst size will be
-    dynamically adjusted to adapt to the network conditions. This parameter is
-    ignored by BBR as pacing is automatically activated for this algorithm.
+    dynamically adjusted to adapt to the network conditions.
 
   Example:
       # newreno congestion control algorithm

diff --git a/src/cfgparse-quic.c b/src/cfgparse-quic.c
index adbd020d2f7f16b768507f284a7a701a30a82fb3..acb7d0d697dcc4015f2336fa4b98716308b60620 100644 (file)
--- a/src/cfgparse-quic.c
+++ b/src/cfgparse-quic.c
@@ -191,11 +191,7 @@ static int bind_parse_quic_cc_algo(char **args, int cur_arg, struct proxy *px,
                        if (pacing < 0)
                                goto fail;
 
-                       if (!(cc_algo->flags & QUIC_CC_ALGO_FL_OPT_PACING)) {
-                               ha_warning("'%s' : pacing parameter ignored for '%s' congestion algorithm\n",
-                                          args[cur_arg], algo);
-                       }
-                       else if (pacing) {
+                       if (pacing) {
                                if (!experimental_directives_allowed) {
                                        memprintf(err, "'%s' : support for pacing is experimental, must be allowed via a global "
                                                  "'expose-experimental-directives'\n", args[cur_arg]);
@@ -204,6 +200,11 @@ static int bind_parse_quic_cc_algo(char **args, int cur_arg, struct proxy *px,
 
                                cc_algo->pacing_inter = quic_cc_default_pacing_inter;
                        }
+                       else if (!(cc_algo->flags & QUIC_CC_ALGO_FL_OPT_PACING)) {
+                               ha_warning("'%s' : '%s' algorithm without pacing may cause slowdowns or high loss rates during transfers\n",
+                                          args[cur_arg], algo);
+                               cc_algo->pacing_inter = NULL;
+                       }
 
                        if (*end_opt == ')') {
                                goto out;