diff --git a/contrib/opentracing/src/http.c b/contrib/opentracing/src/http.c
new file mode 100644
index 0000000..72b31b7
--- /dev/null
+++ b/contrib/opentracing/src/http.c
@@ -0,0 +1,291 @@
+/***
+ * Copyright 2020 HAProxy Technologies
+ *
+ * This file is part of the HAProxy OpenTracing filter.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
+ */
+#include "include.h"
+
+
+#ifdef DEBUG_OT
+
+/***
+ * NAME
+ *   flt_ot_http_headers_dump -
+ *
+ * ARGUMENTS
+ *   chn -
+ *
+ * DESCRIPTION
+ *   -
+ *
+ * RETURN VALUE
+ *   This function does not return a value.
+ */
+void flt_ot_http_headers_dump(const struct channel *chn)
+{
+	const struct htx *htx;
+	int32_t           pos;
+
+	FLT_OT_FUNC("%p", chn);
+
+	if (chn == NULL)
+		FLT_OT_RETURN();
+
+	htx = htxbuf(&(chn->buf));
+
+	if (htx_is_empty(htx))
+		FLT_OT_RETURN();
+
+	for (pos = htx_get_first(htx); pos != -1; pos = htx_get_next(htx, pos)) {
+		struct htx_blk    *blk  = htx_get_blk(htx, pos);
+		enum htx_blk_type  type = htx_get_blk_type(blk);
+
+		if (type == HTX_BLK_HDR) {
+			struct ist n = htx_get_blk_name(htx, blk);
+			struct ist v = htx_get_blk_value(htx, blk);
+
+			FLT_OT_DBG(2, "'%.*s: %.*s'", (int)n.len, n.ptr, (int)v.len, v.ptr);
+		}
+		else if (type == HTX_BLK_EOH)
+			break;
+	}
+
+	FLT_OT_RETURN();
+}
+
+#endif /* DEBUG_OT */
+
+
+/***
+ * NAME
+ *   flt_ot_http_headers_get -
+ *
+ * ARGUMENTS
+ *   chn    -
+ *   prefix -
+ *   len    -
+ *   err    -
+ *
+ * DESCRIPTION
+ *   This function is very similar to function http_action_set_header(), from
+ *   the HAProxy source.
+ *
+ * RETURN VALUE
+ *   -
+ */
+struct otc_text_map *flt_ot_http_headers_get(struct channel *chn, const char *prefix, size_t len, char **err)
+{
+	const struct htx    *htx;
+	size_t               prefix_len = (!FLT_OT_STR_ISVALID(prefix) || (len == 0)) ? 0 : (len + 1);
+	int32_t              pos;
+	struct otc_text_map *retptr = NULL;
+
+	FLT_OT_FUNC("%p, \"%s\", %zu, %p:%p", chn, prefix, len, FLT_OT_DPTR_ARGS(err));
+
+	if (chn == NULL)
+		FLT_OT_RETURN(retptr);
+
+	htx = htxbuf(&(chn->buf));
+
+	for (pos = htx_get_first(htx); pos != -1; pos = htx_get_next(htx, pos)) {
+		struct htx_blk    *blk  = htx_get_blk(htx, pos);
+		enum htx_blk_type  type = htx_get_blk_type(blk);
+
+		if (type == HTX_BLK_HDR) {
+			struct ist v, n = htx_get_blk_name(htx, blk);
+
+			if ((prefix_len == 0) || ((n.len >= prefix_len) && (strncasecmp(n.ptr, prefix, len) == 0))) {
+				if (retptr == NULL) {
+					retptr = otc_text_map_new(NULL, 8);
+					if (retptr == NULL) {
+						FLT_OT_ERR("failed to create HTTP header data");
+
+						break;
+					}
+				}
+
+				v = htx_get_blk_value(htx, blk);
+
+				/*
+				 * Here, an HTTP header (which is actually part
+				 * of the span context is added to the text_map.
+				 *
+				 * Before adding, the prefix is removed from the
+				 * HTTP header name.
+				 */
+				if (otc_text_map_add(retptr, n.ptr + prefix_len, n.len - prefix_len, v.ptr, v.len, OTC_TEXT_MAP_DUP_KEY | OTC_TEXT_MAP_DUP_VALUE) == -1) {
+					FLT_OT_ERR("failed to add HTTP header data");
+
+					otc_text_map_destroy(&retptr, OTC_TEXT_MAP_FREE_KEY | OTC_TEXT_MAP_FREE_VALUE);
+
+					break;
+				}
+			}
+		}
+		else if (type == HTX_BLK_EOH)
+			break;
+	}
+
+	ot_text_map_show(retptr);
+
+	if ((retptr != NULL) && (retptr->count == 0)) {
+		FLT_OT_DBG(2, "WARNING: no HTTP headers found");
+
+		otc_text_map_destroy(&retptr, OTC_TEXT_MAP_FREE_KEY | OTC_TEXT_MAP_FREE_VALUE);
+	}
+
+	FLT_OT_RETURN(retptr);
+}
+
+
+/***
+ * NAME
+ *   flt_ot_http_header_set -
+ *
+ * ARGUMENTS
+ *   chn    -
+ *   prefix -
+ *   name   -
+ *   value  -
+ *   err    -
+ *
+ * DESCRIPTION
+ *   This function is very similar to function http_action_set_header(), from
+ *   the HAProxy source.
+ *
+ * RETURN VALUE
+ *   -
+ */
+int flt_ot_http_header_set(struct channel *chn, const char *prefix, const char *name, const char *value, char **err)
+{
+	struct http_hdr_ctx  ctx = { .blk = NULL };
+	struct ist           ist_name;
+	struct buffer       *buffer = NULL;
+	struct htx          *htx;
+	int                  retval = -1;
+
+	FLT_OT_FUNC("%p, \"%s\", \"%s\", \"%s\", %p:%p", chn, prefix, name, value, FLT_OT_DPTR_ARGS(err));
+
+	if ((chn == NULL) || (!FLT_OT_STR_ISVALID(prefix) && !FLT_OT_STR_ISVALID(name)))
+		FLT_OT_RETURN(retval);
+
+	htx = htxbuf(&(chn->buf));
+
+	/*
+	 * Very rare (about 1% of cases), htx is empty.
+	 * In order to avoid segmentation fault, we exit this function.
+	 */
+	if (htx_is_empty(htx)) {
+		FLT_OT_ERR("HTX is empty");
+
+		FLT_OT_RETURN(retval);
+	}
+
+	if (!FLT_OT_STR_ISVALID(prefix)) {
+		ist_name.ptr = (char *)name;
+		ist_name.len = strlen(name);
+	}
+	else if (!FLT_OT_STR_ISVALID(name)) {
+		ist_name.ptr = (char *)prefix;
+		ist_name.len = strlen(prefix);
+	}
+	else {
+		buffer = flt_ot_trash_alloc(0, err);
+		if (buffer == NULL)
+			FLT_OT_RETURN(retval);
+
+		(void)chunk_printf(buffer, "%s-%s", prefix, name);
+
+		ist_name.ptr = buffer->area;
+		ist_name.len = buffer->data;
+	}
+
+	/* Remove all occurrences of the header. */
+	while (http_find_header(htx, ist(""), &ctx, 1) == 1) {
+		struct ist n = htx_get_blk_name(htx, ctx.blk);
+#ifdef DEBUG_OT
+		struct ist v = htx_get_blk_value(htx, ctx.blk);
+#endif
+
+		/*
+		 * If the <name> parameter is not set, then remove all headers
+		 * that start with the contents of the <prefix> parameter.
+		 */
+		if (!FLT_OT_STR_ISVALID(name))
+			n.len = ist_name.len;
+
+		if (isteqi(n, ist_name))
+			if (http_remove_header(htx, &ctx) == 1)
+				FLT_OT_DBG(3, "HTTP header '%.*s: %.*s' removed", (int)n.len, n.ptr, (int)v.len, v.ptr);
+	}
+
+	/*
+	 * If the value pointer has a value of NULL, the HTTP header is not set
+	 * after deletion.
+	 */
+	if (value == NULL) {
+		/* Do nothing. */
+	}
+	else if (http_add_header(htx, ist_name, ist(value)) == 1) {
+		retval = 0;
+
+		FLT_OT_DBG(3, "HTTP header '%s: %s' added", ist_name.ptr, value);
+	}
+	else {
+		FLT_OT_ERR("failed to set HTTP header '%s: %s'", ist_name.ptr, value);
+	}
+
+	flt_ot_trash_free(&buffer);
+
+	FLT_OT_RETURN(retval);
+}
+
+
+/***
+ * NAME
+ *   flt_ot_http_headers_remove -
+ *
+ * ARGUMENTS
+ *   chn    -
+ *   prefix -
+ *   err    -
+ *
+ * DESCRIPTION
+ *   -
+ *
+ * RETURN VALUE
+ *   -
+ */
+int flt_ot_http_headers_remove(struct channel *chn, const char *prefix, char **err)
+{
+	int retval;
+
+	FLT_OT_FUNC("%p, \"%s\", %p:%p", chn, prefix, FLT_OT_DPTR_ARGS(err));
+
+	retval = flt_ot_http_header_set(chn, prefix, NULL, NULL, err);
+
+	FLT_OT_RETURN(retval);
+}
+
+/*
+ * Local variables:
+ *  c-indent-level: 8
+ *  c-basic-offset: 8
+ * End:
+ *
+ * vi: noexpandtab shiftwidth=8 tabstop=8
+ */