From f349d0b11301b593fb9482f1b4117cb608a46d46 Mon Sep 17 00:00:00 2001
From: Christopher Faulet <cfaulet@haproxy.com>
Date: Thu, 2 Apr 2026 21:47:12 +0200
Subject: [PATCH] MEDIUM: haterm: Add support for splicing and option to
 disable it

The support for the splicing was added and enabled by default, if
supported. The command line option '-dS' was also added to disable the
feature.

When the splicing can be used and the front multiplexer agrees to proceed,
tee() is used to "copy" data from the master pipe to the client pipe.
---
 src/haterm.c      | 22 +++++++++++++++++++++-
 src/haterm_init.c |  9 +++++++++
 2 files changed, 30 insertions(+), 1 deletion(-)

diff --git a/src/haterm.c b/src/haterm.c
index e66c41f23..f7ef4ddbe 100644
--- a/src/haterm.c
+++ b/src/haterm.c
@@ -48,7 +48,8 @@ const char *HTTP_HELP =
         "                     E.g. /?K=1\n"
         " - /?t=<time>        wait <time> milliseconds before responding.\n"
         "                     E.g. /?t=500\n"
-        " - /?k=<enable>      Enable transfer encoding chunked with only one chunk if >0.\n"
+        " - /?k=<enable>      Enable transfer encoding chunked with only one chunk if >0 (disable fast-forward and splicing).\n"
+        " - /?S=<enable>      Disable use of splice() to send data if <1.\n"
         " - /?R=<enable>      Enable sending random data if >0.\n"
         "\n"
         "Note that those arguments may be cumulated on one line separated by a set of\n"
@@ -324,6 +325,10 @@ static int hstream_ff_snd(struct connection *conn, struct hstream *hs)
 	}
 
 	nego_flags |= NEGO_FF_FL_EXACT_SIZE;
+#if defined(USE_LINUX_SPLICE)
+	if ((global.tune.options & GTUNE_USE_SPLICE) && !(sd->iobuf.flags & IOBUF_FL_NO_SPLICING))
+		nego_flags |= NEGO_FF_FL_MAY_SPLICE;
+#endif
 	len = se_nego_ff(sd, &BUF_NULL, hs->to_write, nego_flags);
 	if (sd->iobuf.flags & IOBUF_FL_NO_FF) {
 		TRACE_DEVEL("Fast-forwarding not supported by endpoint, disable it", HS_EV_HSTRM_RESP, hs);
@@ -334,10 +339,25 @@ static int hstream_ff_snd(struct connection *conn, struct hstream *hs)
 		goto out;
 	}
 
+#if defined(USE_LINUX_SPLICE)
+	if (sd->iobuf.pipe) {
+		if (len > master_pipesize)
+			len = master_pipesize;
+		ret = tee(master_pipe->cons, sd->iobuf.pipe->prod, len, SPLICE_F_NONBLOCK);
+		if (ret > 0) {
+			sd->iobuf.pipe->data += ret;
+			hs->to_write -= ret;
+		}
+		if (!hs->to_write)
+			sd->iobuf.flags |= IOBUF_FL_EOI;
+		goto done;
+	}
+#endif
 	hs->to_write -= hstream_add_ff_data(hs, sd, len);
 	if (!hs->to_write)
 		sd->iobuf.flags |= IOBUF_FL_EOI;
 
+  done:
 	if (se_done_ff(sd) != 0 || !(sd->iobuf.flags & (IOBUF_FL_FF_BLOCKED|IOBUF_FL_FF_WANT_ROOM))) {
 		/* Something was forwarding or the consumer states it is not
 		 * blocked anyore, don't reclaim more room */
diff --git a/src/haterm_init.c b/src/haterm_init.c
index 797e636d2..06752c4ca 100644
--- a/src/haterm_init.c
+++ b/src/haterm_init.c
@@ -26,6 +26,7 @@ static void haterm_usage(char *name)
 		"        -c <curves> : ECSDA curves (ex: \"P-256\", \"P-384\"...)\n"
 		"        -v : shows version\n"
 		"        -d : enable the traces for all http protocols\n"
+		"        -dS : disables splice() usage even when available\n"
 		"        -dZ : disable zero-copy forwarding\n"
 		"        --" QUIC_BIND_LONG_OPT " <opts> : append options to QUIC \"bind\" lines\n"
 		"        --" TCP_BIND_LONG_OPT " <opts> : append options to TCP \"bind\" lines\n"
@@ -40,6 +41,9 @@ static void haterm_usage(char *name)
 static const char *haterm_cfg_dflt_str =
         "defaults\n"
             "\tmode haterm\n"
+#if defined(USE_LINUX_SPLICE)
+	    "\toption splice-response\n"
+#endif
             "\ttimeout client 25s\n";
 
 #define HATERM_CFG_CRT_STORE_STR_FMT \
@@ -247,6 +251,11 @@ void haproxy_init_args(int argc, char **argv)
 				else
 					haterm_usage(progname);
 			}
+#if defined(USE_LINUX_SPLICE)
+			else if (*opt == 'd' && *(opt+1) == 'S') {
+				global.tune.options &= ~GTUNE_USE_SPLICE;
+			}
+#endif
 			else if (*opt == 'd' && *(opt+1) == 'Z') {
 				global.tune.no_zero_copy_fwd |= NO_ZERO_COPY_FWD;
 			}