MINOR: quic: implement send-retry quic-initial rules

Define a new quic-initial "send-retry" rule. This allows to force the
emission of a Retry packet on an initial without token instead of
creating a quic_conn.

doc/configuration.txt

@@ -11010,6 +11010,7 @@ quic-initial <action> [ { if | unless } <condition> ]
     - accept
     - dgram-drop
     - reject
+    - send-retry
 
 
 rate-limit sessions <rate>
@@ -14389,6 +14390,7 @@ sc-inc-gpc0                    -           X     X     X     X            X   X
 sc-inc-gpc1                    -           X     X     X     X            X   X   X
 sc-set-gpt                     -           X     X     X     X            X   X   X
 sc-set-gpt0                    -           X     X     X     X            X   X   X
+send-retry                     X           -     -     -     -            -   -   -
 send-spoe-group                -           -     -     X     X            X   X   -
 set-bandwidth-limit            -           -     -     X     X            X   X   -
 set-bc-mark                    -           -     -     X     -            X   -   -
@@ -15263,6 +15265,16 @@ sc-set-gpt0(<sc-id>) { <int> | <expr> }
   See also the "sc-set-gpt" action.
 
 
+send-retry
+  Usable in:  QUIC Ini|    TCP RqCon| RqSes| RqCnt| RsCnt|    HTTP Req| Res| Aft
+                    X |          -  |   -  |   -  |   -  |          - |  - |  -
+
+  This action forces the emission of a Retry packet in response to a client
+  Initial packet without token. This is useful to ensure client address is
+  validated prior to instantiating any connection elements and starting the
+  handshake.
+
+
 send-spoe-group <engine-name> <group-name>
   Usable in:  QUIC Ini|    TCP RqCon| RqSes| RqCnt| RsCnt|    HTTP Req| Res| Aft
                     - |          -  |   -  |   X  |   X  |          X |  X |  -

include/haproxy/quic_sock-t.h

@@ -27,6 +27,7 @@ struct quic_receiver_buf {
 };
 
 #define QUIC_DGRAM_FL_REJECT			0x00000001
+#define QUIC_DGRAM_FL_SEND_RETRY		0x00000002
 
 /* QUIC datagram */
 struct quic_dgram {

src/quic_rules.c

@@ -100,6 +100,14 @@ static enum act_return quic_init_action_reject(struct act_rule *rule, struct pro
 	return ACT_RET_DONE;
 }
 
+static enum act_return quic_init_action_send_retry(struct act_rule *rule, struct proxy *px,
+                                                   struct session *sess, struct stream *s, int flags)
+{
+	struct quic_dgram *dgram = __objt_dgram(sess->origin);
+	dgram->flags |= QUIC_DGRAM_FL_SEND_RETRY;
+	return ACT_RET_DONE;
+}
+
 static enum act_parse_ret parse_reject(const char **args, int *orig_arg,
                                        struct proxy *px,
                                        struct act_rule *rule, char **err)
@@ -109,6 +117,15 @@ static enum act_parse_ret parse_reject(const char **args, int *orig_arg,
 	return ACT_RET_PRS_OK;
 }
 
+static enum act_parse_ret parse_send_retry(const char **args, int *orig_arg,
+                                           struct proxy *px,
+                                           struct act_rule *rule, char **err)
+{
+	rule->action     = ACT_CUSTOM;
+	rule->action_ptr = quic_init_action_send_retry;
+	return ACT_RET_PRS_OK;
+}
+
 /* List head of all known action keywords for "quic-initial" */
 struct action_kw_list quic_init_actions_list = {
        .list = LIST_HEAD_INIT(quic_init_actions_list.list)
@@ -129,6 +146,7 @@ static struct action_kw_list quic_init_actions = { ILH, {
 		{ "accept",           parse_accept,            0 },
 		{ "dgram-drop",       parse_dgram_drop,        0 },
 		{ "reject",           parse_reject,            0 },
+		{ "send-retry",       parse_send_retry,        0 },
 		{ /* END */ },
 	}
 };

src/quic_rx.c

@@ -1615,7 +1615,8 @@ static struct quic_conn *quic_rx_pkt_retrieve_conn(struct quic_rx_packet *pkt,
 			/* No need to emit Retry if connection is refused. */
 			if (!pkt->token_len && !(dgram->flags & QUIC_DGRAM_FL_REJECT)) {
 				if ((l->bind_conf->options & BC_O_QUIC_FORCE_RETRY) ||
-				    HA_ATOMIC_LOAD(&prx_counters->half_open_conn) >= global.tune.quic_retry_threshold) {
+				    HA_ATOMIC_LOAD(&prx_counters->half_open_conn) >= global.tune.quic_retry_threshold ||
+				    (dgram->flags & QUIC_DGRAM_FL_SEND_RETRY)) {
 
 					TRACE_PROTO("Initial without token, sending retry",
 						    QUIC_EV_CONN_LPKT, NULL, NULL, NULL, pkt->version);