Resolver: explicit check for compression pointers in question. Since nginx always uses exactly one entry in the question section of a DNS query, and never uses compression pointers in this entry, parsing of a DNS response in ngx_resolver_process_response() does not expect compression pointers to appear in the question section of the DNS response. Indeed, compression pointers in the first name of a DNS response hardly make sense, do not seem to be allowed by RFC 1035 (which says "a pointer to a prior occurance of the same name", note "prior"), and were never observed in practice. Added an explicit check to ngx_resolver_process_response()'s parsing of the question section to properly report an error if compression pointers nevertheless appear in the question section.

/*
 * Copyright (C) Igor Sysoev
 * Copyright (C) Nginx, Inc.
 */


#ifndef _NGX_MD5_H_INCLUDED_
#define _NGX_MD5_H_INCLUDED_


#include <ngx_config.h>
#include <ngx_core.h>


typedef struct {
    uint64_t  bytes;
    uint32_t  a, b, c, d;
    u_char    buffer[64];
} ngx_md5_t;


void ngx_md5_init(ngx_md5_t *ctx);
void ngx_md5_update(ngx_md5_t *ctx, const void *data, size_t size);
void ngx_md5_final(u_char result[16], ngx_md5_t *ctx);


#endif /* _NGX_MD5_H_INCLUDED_ */