From db6ff84d840e3fb24218bb5c79c151b45d7857c2 Mon Sep 17 00:00:00 2001
From: Frederic Lecaille <flecaille@haproxy.com>
Date: Thu, 21 May 2026 07:32:11 +0200
Subject: [PATCH] to be merged: support again h2c after recent haproxy changes

-- server "proto h2c" could not be used anymore
h2c is not an ALPN identifier, this is a protocol
---
 include/haproxy/haload.h |  2 ++
 src/haload.c             |  8 ++++++--
 src/haload_init.c        | 40 +++++++++++++++++++++++++++++++++++++++-
 3 files changed, 47 insertions(+), 3 deletions(-)

diff --git a/include/haproxy/haload.h b/include/haproxy/haload.h
index b91a78480..04769913e 100644
--- a/include/haproxy/haload.h
+++ b/include/haproxy/haload.h
@@ -14,10 +14,12 @@ struct hld_path {
 
 struct hld_url_cfg {
 	int ssl;
+	int h2c;
 	char *addr;
 	char *raw_addr; // used only to set the host header value
 	char *srv_opts;
 	char *tls_opts;
+	char *alpn;
 	struct server *srv;
 	struct hld_path *paths;
 	struct hld_url_cfg *next;
diff --git a/src/haload.c b/src/haload.c
index 58904e7e7..ab8dd113a 100644
--- a/src/haload.c
+++ b/src/haload.c
@@ -1765,8 +1765,12 @@ static int hld_cfg_finalize(void)
 			}
 		}
 
-		if (!srv->mux_proto && srv_is_quic(srv))
-			srv->mux_proto = get_mux_proto(ist("quic"));
+		if (!srv->mux_proto) {
+			if (srv_is_quic(srv))
+				srv->mux_proto = get_mux_proto(ist("quic"));
+			else if (cfg->h2c)
+				srv->mux_proto = get_mux_proto(ist("h2"));
+		}
 
 		if (srv->mux_proto) {
 			int proto_mode = conn_pr_mode_to_proto_mode(hld_proxy.mode);
diff --git a/src/haload_init.c b/src/haload_init.c
index 83c945ed0..e6f866178 100644
--- a/src/haload_init.c
+++ b/src/haload_init.c
@@ -11,7 +11,8 @@
 
 static int hld_debug;
 struct hld_url_cfg *hld_url_cfgs;
-char *srv_opts, *tls_ciphers, *tls_ciphersuites, *tls_curves;
+char *srv_opts, *tls_ciphers, *tls_ciphersuites, *tls_curves, *alpn;
+int h2c;
 
 static void  hld_usage(char *name, int argc, int line)
 {
@@ -245,9 +246,21 @@ static struct hld_url_cfg *hld_alloc_url(char *url)
 	    !hld_add_opt_to_buf(&opts_buf, "curves", tls_curves))
 		goto err;
 
+	if (alpn && !h2c &&
+	    !hld_add_opt_to_buf(&opts_buf, "alpn", alpn))
+		goto err;
+
 	if (!hbuf_is_null(&opts_buf))
 		hld_url_cfg->tls_opts = strdup(opts_buf.area);
 
+	if (alpn && !h2c) {
+		hld_url_cfg->alpn = strdup(alpn);
+		if (!hld_url_cfg->alpn)
+			goto err;
+	}
+
+	hld_url_cfg->h2c = h2c;
+
 	free_hbuf(&opts_buf);
 	hld_url_cfg->srv = NULL;
 	hld_url_cfg->paths = p;
@@ -415,6 +428,31 @@ void haproxy_init_args(int argc, char **argv)
 				else
 					hld_usage(progname, argc, __LINE__);
 			}
+			else if (strcmp(opt, "0") == 0 ||
+			         strcmp(opt, "h0") == 0) {
+				alpn = "hq-interop";
+				h2c = 0;
+			}
+			else if (strcmp(opt, "1") == 0 ||
+			         strcmp(opt, "h1") == 0) {
+				alpn = "h1";
+				h2c = 0;
+			}
+			else if (strcmp(opt, "2") == 0 ||
+			         strcmp(opt, "h2") == 0) {
+				alpn = "h2";
+				h2c = 0;
+			}
+			else if (strcmp(opt, "2c") == 0 ||
+			         strcmp(opt, "h2c") == 0) {
+				alpn = "h2c";
+				h2c = 1;
+			}
+			else if (strcmp(opt, "3") == 0 ||
+			         strcmp(opt, "h3") == 0) {
+				alpn = "h3";
+				h2c = 0;
+			}
 			else if (*opt == 'd') {
 				opt++;
 				hld_parse_long(&arg_dura, opt, &argc, &argv);