From 52d73aa49799848042c09be1c64c1bff2159a5e1 Mon Sep 17 00:00:00 2001 From: Stefan Hajnoczi Date: Mon, 20 Aug 2012 10:14:35 +0100 Subject: [PATCH] net: EAGAIN handling for net/socket.c TCP Replace spinning send_all() with a proper non-blocking send. When the socket write buffer limit is reached, we should stop trying to send and wait for the socket to become writable again. Non-blocking TCP sockets can return in two different ways when the write buffer limit is reached: 1. ret = -1 and errno = EAGAIN/EWOULDBLOCK. No data has been written. 2. ret < total_size. Short write, only part of the message was transmitted. Handle both cases and keep track of how many bytes have been written in s->send_index. (This includes the 'length' header before the actual payload buffer.) Signed-off-by: Stefan Hajnoczi (cherry picked from commit 45a7f54a8bb3928ffa58d522e0d61acaee8277bb) Signed-off-by: Michael Roth --- net/socket.c | 36 +++++++++++++++++++++++++++++++----- 1 file changed, 31 insertions(+), 5 deletions(-) diff --git a/net/socket.c b/net/socket.c index e5e4e8d..c3e55b8 100644 --- a/net/socket.c +++ b/net/socket.c @@ -32,6 +32,7 @@ #include "qemu-error.h" #include "qemu-option.h" #include "qemu_socket.h" +#include "iov.h" typedef struct NetSocketState { NetClientState nc; @@ -40,6 +41,7 @@ typedef struct NetSocketState { int state; /* 0 = getting length, 1 = getting data */ unsigned int index; unsigned int packet_len; + unsigned int send_index; /* number of bytes sent (only SOCK_STREAM) */ uint8_t buf[4096]; struct sockaddr_in dgram_dst; /* contains inet host and port destination iff connectionless (SOCK_DGRAM) */ IOHandler *send_fn; /* differs between SOCK_STREAM/SOCK_DGRAM */ @@ -88,15 +90,39 @@ static void net_socket_writable(void *opaque) qemu_flush_queued_packets(&s->nc); } -/* XXX: we consider we can send the whole packet without blocking */ static ssize_t net_socket_receive(NetClientState *nc, const uint8_t *buf, size_t size) { NetSocketState *s = DO_UPCAST(NetSocketState, nc, nc); - uint32_t len; - len = htonl(size); + uint32_t len = htonl(size); + struct iovec iov[] = { + { + .iov_base = &len, + .iov_len = sizeof(len), + }, { + .iov_base = (void *)buf, + .iov_len = size, + }, + }; + size_t remaining; + ssize_t ret; + + remaining = iov_size(iov, 2) - s->send_index; + ret = iov_send(s->fd, iov, 2, s->send_index, remaining); - send_all(s->fd, (const uint8_t *)&len, sizeof(len)); - return send_all(s->fd, buf, size); + if (ret == -1 && errno == EAGAIN) { + ret = 0; /* handled further down */ + } + if (ret == -1) { + s->send_index = 0; + return -errno; + } + if (ret < (ssize_t)remaining) { + s->send_index += ret; + net_socket_write_poll(s, true); + return 0; + } + s->send_index = 0; + return size; } static ssize_t net_socket_receive_dgram(NetClientState *nc, const uint8_t *buf, size_t size) -- 1.7.12.1