Mercurial > hg > nginx-quic
view src/core/ngx_rwlock.c @ 8484:3e78c12d4f37 stable-1.20
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.
author | Maxim Dounin <mdounin@mdounin.ru> |
---|---|
date | Tue, 25 May 2021 15:17:50 +0300 |
parents | d1816a2696de |
children | 7752d8523066 |
line wrap: on
line source
/* * Copyright (C) Ruslan Ermilov * Copyright (C) Nginx, Inc. */ #include <ngx_config.h> #include <ngx_core.h> #if (NGX_HAVE_ATOMIC_OPS) #define NGX_RWLOCK_SPIN 2048 #define NGX_RWLOCK_WLOCK ((ngx_atomic_uint_t) -1) void ngx_rwlock_wlock(ngx_atomic_t *lock) { ngx_uint_t i, n; for ( ;; ) { if (*lock == 0 && ngx_atomic_cmp_set(lock, 0, NGX_RWLOCK_WLOCK)) { return; } if (ngx_ncpu > 1) { for (n = 1; n < NGX_RWLOCK_SPIN; n <<= 1) { for (i = 0; i < n; i++) { ngx_cpu_pause(); } if (*lock == 0 && ngx_atomic_cmp_set(lock, 0, NGX_RWLOCK_WLOCK)) { return; } } } ngx_sched_yield(); } } void ngx_rwlock_rlock(ngx_atomic_t *lock) { ngx_uint_t i, n; ngx_atomic_uint_t readers; for ( ;; ) { readers = *lock; if (readers != NGX_RWLOCK_WLOCK && ngx_atomic_cmp_set(lock, readers, readers + 1)) { return; } if (ngx_ncpu > 1) { for (n = 1; n < NGX_RWLOCK_SPIN; n <<= 1) { for (i = 0; i < n; i++) { ngx_cpu_pause(); } readers = *lock; if (readers != NGX_RWLOCK_WLOCK && ngx_atomic_cmp_set(lock, readers, readers + 1)) { return; } } } ngx_sched_yield(); } } void ngx_rwlock_unlock(ngx_atomic_t *lock) { ngx_atomic_uint_t readers; readers = *lock; if (readers == NGX_RWLOCK_WLOCK) { (void) ngx_atomic_cmp_set(lock, NGX_RWLOCK_WLOCK, 0); return; } for ( ;; ) { if (ngx_atomic_cmp_set(lock, readers, readers - 1)) { return; } readers = *lock; } } void ngx_rwlock_downgrade(ngx_atomic_t *lock) { if (*lock == NGX_RWLOCK_WLOCK) { *lock = 1; } } #else #if (NGX_HTTP_UPSTREAM_ZONE || NGX_STREAM_UPSTREAM_ZONE) #error ngx_atomic_cmp_set() is not defined! #endif #endif