MINOR: http-ana: Add a txn flag to support soft/strict message rewrites

the HTTP_MSGF_SOFT_RW flag must now be set on the HTTP transaction to ignore
rewrite errors on a message, from HTTP rules. The mode is called the soft
rewrites. If thes flag is not set, strict rewrites are performed. In this mode,
if a rewrite error occurred, an internal error is reported.

For now, HTTP_MSGF_SOFT_RW is always set and there is no way to switch a
transaction in strict mode.
diff --git a/include/types/http_ana.h b/include/types/http_ana.h
index dd55eb8..a352a99 100644
--- a/include/types/http_ana.h
+++ b/include/types/http_ana.h
@@ -87,7 +87,7 @@
 #define HTTP_MSGF_XFER_LEN    0x00000004  /* message xfer size can be determined */
 #define HTTP_MSGF_VER_11      0x00000008  /* the message is HTTP/1.1 or above */
 
-/* unused: 0x00000010 */
+#define HTTP_MSGF_SOFT_RW     0x00000010  /* soft header rewrites, no error triggered */
 
 #define HTTP_MSGF_COMPRESSING 0x00000020  /* data compression is in progress */
 
diff --git a/src/http_ana.c b/src/http_ana.c
index 5e8d0ab..5b49e34 100644
--- a/src/http_ana.c
+++ b/src/http_ana.c
@@ -3066,6 +3066,11 @@
 						_HA_ATOMIC_ADD(&s->be->be_counters.failed_rewrites, 1);
 					if (sess->listener->counters)
 						_HA_ATOMIC_ADD(&sess->listener->counters->failed_rewrites, 1);
+
+					if (!(txn->req.flags & HTTP_MSGF_SOFT_RW)) {
+						rule_ret = HTTP_RULE_RES_ERROR;
+						goto end;
+					}
 				}
 				free_trash_chunk(replace);
 				break;
@@ -3426,6 +3431,11 @@
 						_HA_ATOMIC_ADD(&sess->listener->counters->failed_rewrites, 1);
 					if (objt_server(s->target))
 						_HA_ATOMIC_ADD(&__objt_server(s->target)->counters.failed_rewrites, 1);
+
+					if (!(txn->rsp.flags & HTTP_MSGF_SOFT_RW)) {
+						rule_ret = HTTP_RULE_RES_ERROR;
+						goto end;
+					}
 				}
 				free_trash_chunk(replace);
 				break;
@@ -5535,13 +5545,13 @@
 
 void http_txn_reset_req(struct http_txn *txn)
 {
-	txn->req.flags = 0;
+	txn->req.flags = HTTP_MSGF_SOFT_RW;
 	txn->req.msg_state = HTTP_MSG_RQBEFORE; /* at the very beginning of the request */
 }
 
 void http_txn_reset_res(struct http_txn *txn)
 {
-	txn->rsp.flags = 0;
+	txn->rsp.flags = HTTP_MSGF_SOFT_RW;
 	txn->rsp.msg_state = HTTP_MSG_RPBEFORE; /* at the very beginning of the response */
 }