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net/vmnet: Pad short Ethernet frames

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At least on macOS 12.7.2, vmnet doesn't pad Ethernet frames, such as the
host's ARP replies, to the minimum size (60 bytes before the frame check
sequence) defined in IEEE Std 802.3-2022, so guests' Ethernet device
drivers may drop them with "frame too short" errors.

This patch calls eth_pad_short_frame() to add padding, as in net/tap.c
and net/slirp.c. Thanks to Bin Meng, Philippe Mathieu-Daudé, and Phil
Dennis-Jordan for reviewing earlier versions.

Signed-off-by: William Hooper <wsh@wshooper.org>
Resolves: https://gitlab.com/qemu-project/qemu/-/issues/2058
Reviewed-by: Phil Dennis-Jordan <phil@philjordan.eu>
Message-ID: <20241102205653.30476-1-wsh@wshooper.org>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
This commit is contained in:
William Hooper 2024-01-06 14:35:46 -08:00 • committed by Philippe Mathieu-Daudé
parent 67e908c936
commit 79b6a98587
1 changed files with 20 additions and 3 deletions
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23
net/vmnet-common.m
View file

@ -18,6 +18,7 @@
#include "qemu/error-report.h"
#include "qapi/error.h"
#include "system/runstate.h"
#include "net/eth.h"
#include <vmnet/vmnet.h>
#include <dispatch/dispatch.h>
@ -147,10 +148,26 @@ static int vmnet_read_packets(VmnetState *s)
*/
static void vmnet_write_packets_to_qemu(VmnetState *s)
{
uint8_t *pkt;
size_t pktsz;
uint8_t min_pkt[ETH_ZLEN];
size_t min_pktsz;
ssize_t size;
while (s->packets_send_current_pos < s->packets_send_end_pos) {
ssize_t size = qemu_send_packet_async(&s->nc,
s->iov_buf[s->packets_send_current_pos].iov_base,
s->packets_buf[s->packets_send_current_pos].vm_pkt_size,
pkt = s->iov_buf[s->packets_send_current_pos].iov_base;
pktsz = s->packets_buf[s->packets_send_current_pos].vm_pkt_size;
if (net_peer_needs_padding(&s->nc)) {
min_pktsz = sizeof(min_pkt);
if (eth_pad_short_frame(min_pkt, &min_pktsz, pkt, pktsz)) {
pkt = min_pkt;
pktsz = min_pktsz;
}
}
size = qemu_send_packet_async(&s->nc, pkt, pktsz,
vmnet_send_completed);
if (size == 0) {