Events: improved error event handling for UDP sockets. Normally, the epoll module calls the read and write handlers depending on whether EPOLLIN and EPOLLOUT are reported by epoll_wait(). No error processing is done in the module, the handlers are expected to get an error when doing I/O. If an error event is reported without EPOLLIN and EPOLLOUT, the module set both EPOLLIN and EPOLLOUT to ensure the error event is handled at least in one active handler. This works well unless the error is delivered along with only one of EPOLLIN or EPOLLOUT, and the corresponding handler does not do any I/O. For example, it happened when getting EPOLLERR|EPOLLOUT from epoll_wait() upon receiving "ICMP port unreachable" while proxying UDP. As the write handler had nothing to send it was not able to detect and log an error, and did not switch to the next upstream. The fix is to unconditionally set EPOLLIN and EPOLLOUT in case of an error event. In the aforementioned case, this causes the read handler to be called which does recv() and detects an error. In addition to the epoll module, analogous changes were made in devpoll/eventport/poll.

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


#ifndef _NGX_ARRAY_H_INCLUDED_
#define _NGX_ARRAY_H_INCLUDED_


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


typedef struct {
    void        *elts;
    ngx_uint_t   nelts;
    size_t       size;
    ngx_uint_t   nalloc;
    ngx_pool_t  *pool;
} ngx_array_t;


ngx_array_t *ngx_array_create(ngx_pool_t *p, ngx_uint_t n, size_t size);
void ngx_array_destroy(ngx_array_t *a);
void *ngx_array_push(ngx_array_t *a);
void *ngx_array_push_n(ngx_array_t *a, ngx_uint_t n);


static ngx_inline ngx_int_t
ngx_array_init(ngx_array_t *array, ngx_pool_t *pool, ngx_uint_t n, size_t size)
{
    /*
     * set "array->nelts" before "array->elts", otherwise MSVC thinks
     * that "array->nelts" may be used without having been initialized
     */

    array->nelts = 0;
    array->size = size;
    array->nalloc = n;
    array->pool = pool;

    array->elts = ngx_palloc(pool, n * size);
    if (array->elts == NULL) {
        return NGX_ERROR;
    }

    return NGX_OK;
}


#endif /* _NGX_ARRAY_H_INCLUDED_ */