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433fdbf8b6
nginx/src/event/modules/ngx_devpoll_module.c
Dmitry Volyntsev 433fdbf8b6 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.
2016-11-21 16:03:42 +03:00

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/*
* Copyright (C) Igor Sysoev
* Copyright (C) Nginx, Inc.
*/
#include <ngx_config.h>
#include <ngx_core.h>
#include <ngx_event.h>
#if (NGX_TEST_BUILD_DEVPOLL)
/* Solaris declarations */
#ifndef POLLREMOVE
#define POLLREMOVE 0x0800
#endif
#define DP_POLL 0xD001
#define DP_ISPOLLED 0xD002
struct dvpoll {
struct pollfd *dp_fds;
int dp_nfds;
int dp_timeout;
};
#endif
typedef struct {
ngx_uint_t changes;
ngx_uint_t events;
} ngx_devpoll_conf_t;
static ngx_int_t ngx_devpoll_init(ngx_cycle_t *cycle, ngx_msec_t timer);
static void ngx_devpoll_done(ngx_cycle_t *cycle);
static ngx_int_t ngx_devpoll_add_event(ngx_event_t *ev, ngx_int_t event,
ngx_uint_t flags);
static ngx_int_t ngx_devpoll_del_event(ngx_event_t *ev, ngx_int_t event,
ngx_uint_t flags);
static ngx_int_t ngx_devpoll_set_event(ngx_event_t *ev, ngx_int_t event,
ngx_uint_t flags);
static ngx_int_t ngx_devpoll_process_events(ngx_cycle_t *cycle,
ngx_msec_t timer, ngx_uint_t flags);
static void *ngx_devpoll_create_conf(ngx_cycle_t *cycle);
static char *ngx_devpoll_init_conf(ngx_cycle_t *cycle, void *conf);
static int dp = -1;
static struct pollfd *change_list, *event_list;
static ngx_uint_t nchanges, max_changes, nevents;
static ngx_event_t **change_index;
static ngx_str_t devpoll_name = ngx_string("/dev/poll");
static ngx_command_t ngx_devpoll_commands[] = {
{ ngx_string("devpoll_changes"),
NGX_EVENT_CONF|NGX_CONF_TAKE1,
ngx_conf_set_num_slot,
0,
offsetof(ngx_devpoll_conf_t, changes),
NULL },
{ ngx_string("devpoll_events"),
NGX_EVENT_CONF|NGX_CONF_TAKE1,
ngx_conf_set_num_slot,
0,
offsetof(ngx_devpoll_conf_t, events),
NULL },
ngx_null_command
};
ngx_event_module_t ngx_devpoll_module_ctx = {
&devpoll_name,
ngx_devpoll_create_conf, /* create configuration */
ngx_devpoll_init_conf, /* init configuration */
{
ngx_devpoll_add_event, /* add an event */
ngx_devpoll_del_event, /* delete an event */
ngx_devpoll_add_event, /* enable an event */
ngx_devpoll_del_event, /* disable an event */
NULL, /* add an connection */
NULL, /* delete an connection */
NULL, /* trigger a notify */
ngx_devpoll_process_events, /* process the events */
ngx_devpoll_init, /* init the events */
ngx_devpoll_done, /* done the events */
}
};
ngx_module_t ngx_devpoll_module = {
NGX_MODULE_V1,
&ngx_devpoll_module_ctx, /* module context */
ngx_devpoll_commands, /* module directives */
NGX_EVENT_MODULE, /* module type */
NULL, /* init master */
NULL, /* init module */
NULL, /* init process */
NULL, /* init thread */
NULL, /* exit thread */
NULL, /* exit process */
NULL, /* exit master */
NGX_MODULE_V1_PADDING
};
static ngx_int_t
ngx_devpoll_init(ngx_cycle_t *cycle, ngx_msec_t timer)
{
size_t n;
ngx_devpoll_conf_t *dpcf;
dpcf = ngx_event_get_conf(cycle->conf_ctx, ngx_devpoll_module);
if (dp == -1) {
dp = open("/dev/poll", O_RDWR);
if (dp == -1) {
ngx_log_error(NGX_LOG_EMERG, cycle->log, ngx_errno,
"open(/dev/poll) failed");
return NGX_ERROR;
}
}
if (max_changes < dpcf->changes) {
if (nchanges) {
n = nchanges * sizeof(struct pollfd);
if (write(dp, change_list, n) != (ssize_t) n) {
ngx_log_error(NGX_LOG_ALERT, cycle->log, ngx_errno,
"write(/dev/poll) failed");
return NGX_ERROR;
}
nchanges = 0;
}
if (change_list) {
ngx_free(change_list);
}
change_list = ngx_alloc(sizeof(struct pollfd) * dpcf->changes,
cycle->log);
if (change_list == NULL) {
return NGX_ERROR;
}
if (change_index) {
ngx_free(change_index);
}
change_index = ngx_alloc(sizeof(ngx_event_t *) * dpcf->changes,
cycle->log);
if (change_index == NULL) {
return NGX_ERROR;
}
}
max_changes = dpcf->changes;
if (nevents < dpcf->events) {
if (event_list) {
ngx_free(event_list);
}
event_list = ngx_alloc(sizeof(struct pollfd) * dpcf->events,
cycle->log);
if (event_list == NULL) {
return NGX_ERROR;
}
}
nevents = dpcf->events;
ngx_io = ngx_os_io;
ngx_event_actions = ngx_devpoll_module_ctx.actions;
ngx_event_flags = NGX_USE_LEVEL_EVENT|NGX_USE_FD_EVENT;
return NGX_OK;
}
static void
ngx_devpoll_done(ngx_cycle_t *cycle)
{
if (close(dp) == -1) {
ngx_log_error(NGX_LOG_ALERT, cycle->log, ngx_errno,
"close(/dev/poll) failed");
}
dp = -1;
ngx_free(change_list);
ngx_free(event_list);
ngx_free(change_index);
change_list = NULL;
event_list = NULL;
change_index = NULL;
max_changes = 0;
nchanges = 0;
nevents = 0;
}
static ngx_int_t
ngx_devpoll_add_event(ngx_event_t *ev, ngx_int_t event, ngx_uint_t flags)
{
#if (NGX_DEBUG)
ngx_connection_t *c;
#endif
#if (NGX_READ_EVENT != POLLIN)
event = (event == NGX_READ_EVENT) ? POLLIN : POLLOUT;
#endif
#if (NGX_DEBUG)
c = ev->data;
ngx_log_debug2(NGX_LOG_DEBUG_EVENT, ev->log, 0,
"devpoll add event: fd:%d ev:%04Xi", c->fd, event);
#endif
ev->active = 1;
return ngx_devpoll_set_event(ev, event, 0);
}
static ngx_int_t
ngx_devpoll_del_event(ngx_event_t *ev, ngx_int_t event, ngx_uint_t flags)
{
ngx_event_t *e;
ngx_connection_t *c;
c = ev->data;
#if (NGX_READ_EVENT != POLLIN)
event = (event == NGX_READ_EVENT) ? POLLIN : POLLOUT;
#endif
ngx_log_debug2(NGX_LOG_DEBUG_EVENT, ev->log, 0,
"devpoll del event: fd:%d ev:%04Xi", c->fd, event);
if (ngx_devpoll_set_event(ev, POLLREMOVE, flags) == NGX_ERROR) {
return NGX_ERROR;
}
ev->active = 0;
if (flags & NGX_CLOSE_EVENT) {
e = (event == POLLIN) ? c->write : c->read;
if (e) {
e->active = 0;
}
return NGX_OK;
}
/* restore the pair event if it exists */
if (event == POLLIN) {
e = c->write;
event = POLLOUT;
} else {
e = c->read;
event = POLLIN;
}
if (e && e->active) {
return ngx_devpoll_set_event(e, event, 0);
}
return NGX_OK;
}
static ngx_int_t
ngx_devpoll_set_event(ngx_event_t *ev, ngx_int_t event, ngx_uint_t flags)
{
size_t n;
ngx_connection_t *c;
c = ev->data;
ngx_log_debug3(NGX_LOG_DEBUG_EVENT, ev->log, 0,
"devpoll fd:%d ev:%04Xi fl:%04Xi", c->fd, event, flags);
if (nchanges >= max_changes) {
ngx_log_error(NGX_LOG_WARN, ev->log, 0,
"/dev/pool change list is filled up");
n = nchanges * sizeof(struct pollfd);
if (write(dp, change_list, n) != (ssize_t) n) {
ngx_log_error(NGX_LOG_ALERT, ev->log, ngx_errno,
"write(/dev/poll) failed");
return NGX_ERROR;
}
nchanges = 0;
}
change_list[nchanges].fd = c->fd;
change_list[nchanges].events = (short) event;
change_list[nchanges].revents = 0;
change_index[nchanges] = ev;
ev->index = nchanges;
nchanges++;
if (flags & NGX_CLOSE_EVENT) {
n = nchanges * sizeof(struct pollfd);
if (write(dp, change_list, n) != (ssize_t) n) {
ngx_log_error(NGX_LOG_ALERT, ev->log, ngx_errno,
"write(/dev/poll) failed");
return NGX_ERROR;
}
nchanges = 0;
}
return NGX_OK;
}
ngx_int_t
ngx_devpoll_process_events(ngx_cycle_t *cycle, ngx_msec_t timer,
ngx_uint_t flags)
{
int events, revents, rc;
size_t n;
ngx_fd_t fd;
ngx_err_t err;
ngx_int_t i;
ngx_uint_t level, instance;
ngx_event_t *rev, *wev;
ngx_queue_t *queue;
ngx_connection_t *c;
struct pollfd pfd;
struct dvpoll dvp;
/* NGX_TIMER_INFINITE == INFTIM */
ngx_log_debug1(NGX_LOG_DEBUG_EVENT, cycle->log, 0,
"devpoll timer: %M", timer);
if (nchanges) {
n = nchanges * sizeof(struct pollfd);
if (write(dp, change_list, n) != (ssize_t) n) {
ngx_log_error(NGX_LOG_ALERT, cycle->log, ngx_errno,
"write(/dev/poll) failed");
return NGX_ERROR;
}
nchanges = 0;
}
dvp.dp_fds = event_list;
dvp.dp_nfds = (int) nevents;
dvp.dp_timeout = timer;
events = ioctl(dp, DP_POLL, &dvp);
err = (events == -1) ? ngx_errno : 0;
if (flags & NGX_UPDATE_TIME || ngx_event_timer_alarm) {
ngx_time_update();
}
if (err) {
if (err == NGX_EINTR) {
if (ngx_event_timer_alarm) {
ngx_event_timer_alarm = 0;
return NGX_OK;
}
level = NGX_LOG_INFO;
} else {
level = NGX_LOG_ALERT;
}
ngx_log_error(level, cycle->log, err, "ioctl(DP_POLL) failed");
return NGX_ERROR;
}
if (events == 0) {
if (timer != NGX_TIMER_INFINITE) {
return NGX_OK;
}
ngx_log_error(NGX_LOG_ALERT, cycle->log, 0,
"ioctl(DP_POLL) returned no events without timeout");
return NGX_ERROR;
}
for (i = 0; i < events; i++) {
fd = event_list[i].fd;
revents = event_list[i].revents;
c = ngx_cycle->files[fd];
if (c == NULL || c->fd == -1) {
pfd.fd = fd;
pfd.events = 0;
pfd.revents = 0;
rc = ioctl(dp, DP_ISPOLLED, &pfd);
switch (rc) {
case -1:
ngx_log_error(NGX_LOG_ALERT, cycle->log, ngx_errno,
"ioctl(DP_ISPOLLED) failed for socket %d, event %04Xd",
fd, revents);
break;
case 0:
ngx_log_error(NGX_LOG_ALERT, cycle->log, 0,
"phantom event %04Xd for closed and removed socket %d",
revents, fd);
break;
default:
ngx_log_error(NGX_LOG_ALERT, cycle->log, 0,
"unexpected event %04Xd for closed and removed socket %d, "
"ioctl(DP_ISPOLLED) returned rc:%d, fd:%d, event %04Xd",
revents, fd, rc, pfd.fd, pfd.revents);
pfd.fd = fd;
pfd.events = POLLREMOVE;
pfd.revents = 0;
if (write(dp, &pfd, sizeof(struct pollfd))
!= (ssize_t) sizeof(struct pollfd))
{
ngx_log_error(NGX_LOG_ALERT, cycle->log, ngx_errno,
"write(/dev/poll) for %d failed", fd);
}
if (close(fd) == -1) {
ngx_log_error(NGX_LOG_ALERT, cycle->log, ngx_errno,
"close(%d) failed", fd);
}
break;
}
continue;
}
ngx_log_debug3(NGX_LOG_DEBUG_EVENT, cycle->log, 0,
"devpoll: fd:%d, ev:%04Xd, rev:%04Xd",
fd, event_list[i].events, revents);
if (revents & (POLLERR|POLLHUP|POLLNVAL)) {
ngx_log_debug3(NGX_LOG_DEBUG_EVENT, cycle->log, 0,
"ioctl(DP_POLL) error fd:%d ev:%04Xd rev:%04Xd",
fd, event_list[i].events, revents);
}
if (revents & ~(POLLIN|POLLOUT|POLLERR|POLLHUP|POLLNVAL)) {
ngx_log_error(NGX_LOG_ALERT, cycle->log, 0,
"strange ioctl(DP_POLL) events "
"fd:%d ev:%04Xd rev:%04Xd",
fd, event_list[i].events, revents);
}
if (revents & (POLLERR|POLLHUP|POLLNVAL)) {
/*
* if the error events were returned, add POLLIN and POLLOUT
* to handle the events at least in one active handler
*/
revents |= POLLIN|POLLOUT;
}
rev = c->read;
if ((revents & POLLIN) && rev->active) {
rev->ready = 1;
if (flags & NGX_POST_EVENTS) {
queue = rev->accept ? &ngx_posted_accept_events
: &ngx_posted_events;
ngx_post_event(rev, queue);
} else {
instance = rev->instance;
rev->handler(rev);
if (c->fd == -1 || rev->instance != instance) {
continue;
}
}
}
wev = c->write;
if ((revents & POLLOUT) && wev->active) {
wev->ready = 1;
if (flags & NGX_POST_EVENTS) {
ngx_post_event(wev, &ngx_posted_events);
} else {
wev->handler(wev);
}
}
}
return NGX_OK;
}
static void *
ngx_devpoll_create_conf(ngx_cycle_t *cycle)
{
ngx_devpoll_conf_t *dpcf;
dpcf = ngx_palloc(cycle->pool, sizeof(ngx_devpoll_conf_t));
if (dpcf == NULL) {
return NULL;
}
dpcf->changes = NGX_CONF_UNSET;
dpcf->events = NGX_CONF_UNSET;
return dpcf;
}
static char *
ngx_devpoll_init_conf(ngx_cycle_t *cycle, void *conf)
{
ngx_devpoll_conf_t *dpcf = conf;
ngx_conf_init_uint_value(dpcf->changes, 32);
ngx_conf_init_uint_value(dpcf->events, 32);
return NGX_CONF_OK;
}
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