Mercurial > hg > nginx
view src/os/unix/ngx_readv_chain.c @ 8018:5119c8150478
Fixed runtime handling of systems without EPOLLRDHUP support.
In 7583:efd71d49bde0 (nginx 1.17.5) along with introduction of the
ioctl(FIONREAD) support proper handling of systems without EPOLLRDHUP
support in the kernel (but with EPOLLRDHUP in headers) was broken.
Before the change, rev->available was never set to 0 unless
ngx_use_epoll_rdhup was also set (that is, runtime test for EPOLLRDHUP
introduced in 6536:f7849bfb6d21 succeeded). After the change,
rev->available might reach 0 on systems without runtime EPOLLRDHUP
support, stopping further reading in ngx_readv_chain() and ngx_unix_recv().
And, if EOF happened to be already reported along with the last event,
it is not reported again by epoll_wait(), leading to connection hangs
and timeouts on such systems.
This affects Linux kernels before 2.6.17 if nginx was compiled
with newer headers, and, more importantly, emulation layers, such as
DigitalOcean's App Platform's / gVisor's epoll emulation layer.
Fix is to explicitly check ngx_use_epoll_rdhup before the corresponding
rev->pending_eof tests in ngx_readv_chain() and ngx_unix_recv().
author | Marcus Ball <marcus.ball@live.com> |
---|---|
date | Mon, 30 May 2022 02:38:07 +0300 |
parents | 7f5e3595caff |
children | f3510cb959d1 |
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/* * Copyright (C) Igor Sysoev * Copyright (C) Nginx, Inc. */ #include <ngx_config.h> #include <ngx_core.h> #include <ngx_event.h> ssize_t ngx_readv_chain(ngx_connection_t *c, ngx_chain_t *chain, off_t limit) { u_char *prev; ssize_t n, size; ngx_err_t err; ngx_array_t vec; ngx_event_t *rev; struct iovec *iov, iovs[NGX_IOVS_PREALLOCATE]; rev = c->read; #if (NGX_HAVE_KQUEUE) if (ngx_event_flags & NGX_USE_KQUEUE_EVENT) { ngx_log_debug3(NGX_LOG_DEBUG_EVENT, c->log, 0, "readv: eof:%d, avail:%d, err:%d", rev->pending_eof, rev->available, rev->kq_errno); if (rev->available == 0) { if (rev->pending_eof) { rev->ready = 0; rev->eof = 1; ngx_log_error(NGX_LOG_INFO, c->log, rev->kq_errno, "kevent() reported about an closed connection"); if (rev->kq_errno) { rev->error = 1; ngx_set_socket_errno(rev->kq_errno); return NGX_ERROR; } return 0; } else { return NGX_AGAIN; } } } #endif #if (NGX_HAVE_EPOLLRDHUP) if ((ngx_event_flags & NGX_USE_EPOLL_EVENT) && ngx_use_epoll_rdhup) { ngx_log_debug2(NGX_LOG_DEBUG_EVENT, c->log, 0, "readv: eof:%d, avail:%d", rev->pending_eof, rev->available); if (rev->available == 0 && !rev->pending_eof) { return NGX_AGAIN; } } #endif prev = NULL; iov = NULL; size = 0; vec.elts = iovs; vec.nelts = 0; vec.size = sizeof(struct iovec); vec.nalloc = NGX_IOVS_PREALLOCATE; vec.pool = c->pool; /* coalesce the neighbouring bufs */ while (chain) { n = chain->buf->end - chain->buf->last; if (limit) { if (size >= limit) { break; } if (size + n > limit) { n = (ssize_t) (limit - size); } } if (prev == chain->buf->last) { iov->iov_len += n; } else { if (vec.nelts == vec.nalloc) { break; } iov = ngx_array_push(&vec); if (iov == NULL) { return NGX_ERROR; } iov->iov_base = (void *) chain->buf->last; iov->iov_len = n; } size += n; prev = chain->buf->end; chain = chain->next; } ngx_log_debug2(NGX_LOG_DEBUG_EVENT, c->log, 0, "readv: %ui, last:%uz", vec.nelts, iov->iov_len); do { n = readv(c->fd, (struct iovec *) vec.elts, vec.nelts); if (n == 0) { rev->ready = 0; rev->eof = 1; #if (NGX_HAVE_KQUEUE) /* * on FreeBSD readv() may return 0 on closed socket * even if kqueue reported about available data */ if (ngx_event_flags & NGX_USE_KQUEUE_EVENT) { rev->available = 0; } #endif return 0; } if (n > 0) { #if (NGX_HAVE_KQUEUE) if (ngx_event_flags & NGX_USE_KQUEUE_EVENT) { rev->available -= n; /* * rev->available may be negative here because some additional * bytes may be received between kevent() and readv() */ if (rev->available <= 0) { if (!rev->pending_eof) { rev->ready = 0; } rev->available = 0; } return n; } #endif #if (NGX_HAVE_FIONREAD) if (rev->available >= 0) { rev->available -= n; /* * negative rev->available means some additional bytes * were received between kernel notification and readv(), * and therefore ev->ready can be safely reset even for * edge-triggered event methods */ if (rev->available < 0) { rev->available = 0; rev->ready = 0; } ngx_log_debug1(NGX_LOG_DEBUG_EVENT, c->log, 0, "readv: avail:%d", rev->available); } else if (n == size) { if (ngx_socket_nread(c->fd, &rev->available) == -1) { n = ngx_connection_error(c, ngx_socket_errno, ngx_socket_nread_n " failed"); break; } ngx_log_debug1(NGX_LOG_DEBUG_EVENT, c->log, 0, "readv: avail:%d", rev->available); } #endif #if (NGX_HAVE_EPOLLRDHUP) if ((ngx_event_flags & NGX_USE_EPOLL_EVENT) && ngx_use_epoll_rdhup) { if (n < size) { if (!rev->pending_eof) { rev->ready = 0; } rev->available = 0; } return n; } #endif if (n < size && !(ngx_event_flags & NGX_USE_GREEDY_EVENT)) { rev->ready = 0; } return n; } err = ngx_socket_errno; if (err == NGX_EAGAIN || err == NGX_EINTR) { ngx_log_debug0(NGX_LOG_DEBUG_EVENT, c->log, err, "readv() not ready"); n = NGX_AGAIN; } else { n = ngx_connection_error(c, err, "readv() failed"); break; } } while (err == NGX_EINTR); rev->ready = 0; if (n == NGX_ERROR) { c->read->error = 1; } return n; }