BUG/MINOR: h1: Report the right error position when a header value is invalid

During H1 messages parsing, when the parser has finished to parse a full header
line, some tests are performed on its value, depending on its name, to be sure
it is valid. The content-length is checked and converted in integer and the host
header is also checked. If an error occurred during this step, the error
position must point on the header value. But from the parser point of view, we
are already on the start of the next header. Thus the effective reported
position in the error capture is the beginning of the unparsed header line. It
is a bit confusing when we try to figure out why a message is rejected.

Now, the parser state is updated to point on the invalid value. This way, the
error position really points on the right position.

This patch must be backported as far as 1.9.

src/h1.c

@@ -819,6 +819,7 @@ int h1_headers_to_hdr_list(char *start, const char *stop,
 
 					if (ret < 0) {
 						state = H1_MSG_HDR_L2_LWS;
+						ptr = v.ptr; /* Set ptr on the error */
 						goto http_msg_invalid;
 					}
 					else if (ret == 0) {
@@ -841,16 +842,18 @@ int h1_headers_to_hdr_list(char *start, const char *stop,
 						if (authority.len && !isteqi(v, authority)) {
 							if (h1m->err_pos < -1) {
 								state = H1_MSG_HDR_L2_LWS;
+								ptr = v.ptr; /* Set ptr on the error */
 								goto http_msg_invalid;
 							}
 							if (h1m->err_pos == -1) /* capture the error pointer */
-								h1m->err_pos = ptr - start + skip; /* >= 0 now */
+								h1m->err_pos = v.ptr - start + skip; /* >= 0 now */
 						}
 						host_idx = hdr_count;
 					}
 					else {
 						if (!isteqi(v, hdr[host_idx].v)) {
 							state = H1_MSG_HDR_L2_LWS;
+							ptr = v.ptr; /* Set ptr on the error */
 							goto http_msg_invalid;
 						}
 						/* if the same host, skip it */