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[Qemu-devel] [PATCH 13/13] net: EAGAIN handling for net/socket.c TCP
From: |
Stefan Hajnoczi |
Subject: |
[Qemu-devel] [PATCH 13/13] net: EAGAIN handling for net/socket.c TCP |
Date: |
Mon, 10 Sep 2012 10:55:36 +0100 |
From: Stefan Hajnoczi <address@hidden>
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 <address@hidden>
---
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)
--
1.7.10.4
- [Qemu-devel] [PULL 00/13] Net patches, Stefan Hajnoczi, 2012/09/14
- [Qemu-devel] [PULL 00/13] Net patches, Stefan Hajnoczi, 2012/09/14
- [Qemu-devel] [PATCH 02/13] e1000: flush queue whenever can_receive can go from false to true, Stefan Hajnoczi, 2012/09/14
- [Qemu-devel] [PATCH 01/13] net: notify iothread after flushing queue, Stefan Hajnoczi, 2012/09/14
- [Qemu-devel] [PATCH 03/13] xen: flush queue when getting an event, Stefan Hajnoczi, 2012/09/14
- [Qemu-devel] [PATCH 04/13] eepro100: Fix network hang when rx buffers run out, Stefan Hajnoczi, 2012/09/14
- [Qemu-devel] [PATCH 05/13] net: add receive_disabled logic to iov delivery path, Stefan Hajnoczi, 2012/09/14
- [Qemu-devel] [PATCH 07/13] net: add -netdev options to man page, Stefan Hajnoczi, 2012/09/14
- [Qemu-devel] [PATCH 08/13] net: clean up usbnet_receive(), Stefan Hajnoczi, 2012/09/14