Do not move body during encode trailers

Trailers should be placed after body, so we should not
move body to the next skb, just allocate new one and use
it.
During work on #2136 we should try to remove/rework this
part of code, because it is better to not move body at all.

Closes #2391

Author: EvgeniiMekhanik

fw/http2.c

@@ -486,7 +486,13 @@ tfw_h2_hpack_encode_trailer_headers(TfwHttpResp *resp)
 	TfwHttpHdrMap *map = resp->mit.map;
 	TfwHttpHdrTbl *ht = resp->h_tbl;
 	unsigned int i;
-	int r;
+	int r = 0;
+
+	/*
+	 * TODO #2136: Remove this flag during reworking
+	 * `tfw_http_msg_expand_from_pool` function. 
+	 */
+	__set_bit(TFW_HTTP_B_RESP_ENCODE_TRAILERS, resp->flags);
 
 	for (i = map->trailer_idx; i < map->count; ++i) {
 		unsigned short hid = map->index[i].idx;
@@ -499,17 +505,22 @@ tfw_h2_hpack_encode_trailer_headers(TfwHttpResp *resp)
 		if (WARN_ON_ONCE(!tgt
 				 || TFW_STR_EMPTY(tgt)
 				 || TFW_STR_DUP(tgt)))
-			return -EINVAL;
+		{
+			r = -EINVAL;
+			goto finish;
+		}
 
 		T_DBG3("%s: hid=%hu, d_num=%hu, nchunks=%u\n",
 		       __func__, hid, d_num, ht->tbl[hid].nchunks);
 
 		r = tfw_hpack_transform(resp, tgt);
 		if (unlikely(r))
-			return r;
+			goto finish;
 	}
 
-	return 0;
+finish:
+	clear_bit(TFW_HTTP_B_RESP_ENCODE_TRAILERS, resp->flags);
+	return r;
 }
 
 int

fw/http_msg.c

@@ -1254,7 +1254,15 @@ __tfw_http_msg_expand_from_pool(TfwHttpMsg *hm, const TfwStr *str,
 				if (!nskb)
 					return -ENOMEM;
 
-				if (hm->body.len > 0) {
+				/*
+				 * TODO #2136: Remove this flag during reworking
+				 * this function. Try to process headers and
+				 * trailers without moving body.
+				 */
+				if (hm->body.len > 0
+			            && !test_bit(TFW_HTTP_B_RESP_ENCODE_TRAILERS,
+						 resp->flags))
+				{
 					r = __tfw_http_msg_move_body(resp, nskb,
 								     &frag);
 					if (unlikely(r < 0)) {

fw/http_types.h

@@ -151,6 +151,9 @@ enum {
 	/* This is 100-continue response. */
 	TFW_HTTP_B_CONTINUE_RESP,
 
+        /* This response is during trailers encoding. */
+        TFW_HTTP_B_RESP_ENCODE_TRAILERS,
+
         _TFW_HTTP_FLAGS_NUM
 };
 

fw/t/unit/test_http_msg.c

@@ -271,10 +271,75 @@ TEST(http_msg, expand_from_pool_for_headers)
 	tfw_http_msg_free((TfwHttpMsg *)resp);
 }
 
+TEST(http_msg, expand_from_pool_for_trailers)
+{
+	static TfwStr frags[] = {
+		TFW_STR_STRING("trailers"),
+		TFW_STR_STRING("headers"),
+		TFW_STR_STRING("paged_body")
+	};
+	TfwStr *trailer = &frags[0], *head = &frags[1], *pgd = &frags[2];
+	TfwHttpResp *resp = __test_resp_alloc(head, pgd, MAX_SKB_FRAGS - 1);
+	TfwHttpMsg *msg = (TfwHttpMsg *)resp;
+	TfwHttpMsgCleanup cleanup = {};
+	TfwMsgIter *it;
+	int i;
+
+	EXPECT_NOT_NULL(resp);
+	if (!resp)
+		return;
+
+	it = &resp->iter;
+	set_bit(TFW_HTTP_B_CHUNKED, resp->flags);
+	resp->body.data = skb_frag_address(&skb_shinfo(it->skb)->frags[0]);
+	resp->body_start_data = skb_frag_address(&skb_shinfo(it->skb)->frags[0]);
+	resp->body_start_skb = it->skb;
+	resp->body.len = (MAX_SKB_FRAGS - 1) * SLEN("paged_body");
+
+	EXPECT_EQ(tfw_http_msg_cutoff_headers(msg, &cleanup), 0);
+
+	/* Linear part MUST be moved to paged fragments */
+	EXPECT_TRUE(!skb_headlen(it->skb));
+	EXPECT_NULL(cleanup.skb_head);
+
+	it->frag = skb_shinfo(it->skb)->nr_frags - 1;
+	tfw_http_msg_setup_transform_pool(&resp->mit, it, resp->pool);
+
+	__set_bit(TFW_HTTP_B_RESP_ENCODE_TRAILERS, resp->flags);
+
+	EXPECT_EQ(tfw_http_msg_expand_from_pool(msg, trailer), 0);
+	EXPECT_EQ(tfw_http_msg_expand_from_pool(msg, trailer), 0);
+
+	clear_bit(TFW_HTTP_B_RESP_ENCODE_TRAILERS, resp->flags);
+
+	for (i = 0; i < MAX_SKB_FRAGS - 1; i++) {
+		skb_frag_t *frag = &skb_shinfo(resp->msg.skb_head)->frags[i];
+		char* addr = skb_frag_address(frag);
+		unsigned int fragsz = skb_frag_size(frag);
+
+		EXPECT_ZERO(memcmp(addr, pgd->data, fragsz));
+	}
+
+	EXPECT_TRUE(resp->msg.skb_head != resp->msg.skb_head->next);
+	EXPECT_TRUE(resp->msg.skb_head->next->next == resp->msg.skb_head);
+	EXPECT_EQ(skb_shinfo(resp->msg.skb_head->next)->nr_frags, 1);
+
+	{
+		skb_frag_t *frag = &skb_shinfo(resp->msg.skb_head->next)->frags[0];
+		char* addr = skb_frag_address(frag);
+		unsigned int fragsz = skb_frag_size(frag);
+
+		EXPECT_ZERO(memcmp(addr, "trailerstrailers", fragsz));
+	}
+
+	tfw_http_msg_free((TfwHttpMsg *)resp);
+}
+
 TEST_SUITE(http_msg)
 {
 	TEST_RUN(http_msg, hdr_in_array);
 	TEST_RUN(http_msg, cutoff_linear_headers_paged_body);
 	TEST_RUN(http_msg, cutoff_linear_headers_and_linear_body);
 	TEST_RUN(http_msg, expand_from_pool_for_headers);
+	TEST_RUN(http_msg, expand_from_pool_for_trailers);
 }