[v1] net/vmnet: Pad short Ethernet frames

[PATCH] net/vmnet: Pad short Ethernet frames

Posted by William Hooper 10 months, 3 weeks ago

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.

Resolves: https://gitlab.com/qemu-project/qemu/-/issues/2058
Signed-off-by: William Hooper <wsh@wshooper.org>
---
 net/vmnet-common.m | 20 +++++++++++++++++---
 1 file changed, 17 insertions(+), 3 deletions(-)

diff --git a/net/vmnet-common.m b/net/vmnet-common.m
index 2958283485..f8f7163226 100644
--- a/net/vmnet-common.m
+++ b/net/vmnet-common.m
@@ -18,6 +18,7 @@
 #include "qemu/error-report.h"
 #include "qapi/error.h"
 #include "sysemu/runstate.h"
+#include "net/eth.h"
 
 #include <vmnet/vmnet.h>
 #include <dispatch/dispatch.h>
@@ -150,10 +151,23 @@ 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 = sizeof(min_pkt);
+
     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)) {
+            if (eth_pad_short_frame(min_pkt, &min_pktsz, pkt, pktsz)) {
+                pkt = min_pkt;
+                pktsz = min_pktsz;
+            }
+        }
+
+        ssize_t size = qemu_send_packet_async(&s->nc, pkt, pktsz,
                                       vmnet_send_completed);
 
         if (size == 0) {
-- 
2.37.1

Re: [PATCH] net/vmnet: Pad short Ethernet frames

Posted by Philippe Mathieu-Daudé 10 months, 3 weeks ago

Hi William,

On 6/1/24 23:35, William Hooper wrote:
> 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.
> 
> Resolves: https://gitlab.com/qemu-project/qemu/-/issues/2058
> Signed-off-by: William Hooper <wsh@wshooper.org>
> ---
>   net/vmnet-common.m | 20 +++++++++++++++++---
>   1 file changed, 17 insertions(+), 3 deletions(-)
> 
> diff --git a/net/vmnet-common.m b/net/vmnet-common.m
> index 2958283485..f8f7163226 100644
> --- a/net/vmnet-common.m
> +++ b/net/vmnet-common.m
> @@ -18,6 +18,7 @@
>   #include "qemu/error-report.h"
>   #include "qapi/error.h"
>   #include "sysemu/runstate.h"
> +#include "net/eth.h"
>   
>   #include <vmnet/vmnet.h>
>   #include <dispatch/dispatch.h>
> @@ -150,10 +151,23 @@ 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 = sizeof(min_pkt);
> +
>       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)) {

Don't we want to initialize min_pktsz here ...

               min_pktsz = sizeof(min_pkt);

> +            if (eth_pad_short_frame(min_pkt, &min_pktsz, pkt, pktsz)) {

... because eth_pad_short_frame() update it?

> +                pkt = min_pkt;
> +                pktsz = min_pktsz;
> +            }
> +        }
> +
> +        ssize_t size = qemu_send_packet_async(&s->nc, pkt, pktsz,
>                                         vmnet_send_completed);
>   
>           if (size == 0) {

Re: [PATCH] net/vmnet: Pad short Ethernet frames

Posted by William Hooper 10 months, 3 weeks ago

On Mon, Jan 8, 2024 at 7:36 AM Philippe Mathieu-Daudé <philmd@linaro.org> wrote:
> Don't we want to initialize min_pktsz here ...
>
>                min_pktsz = sizeof(min_pkt);
>
> > +            if (eth_pad_short_frame(min_pkt, &min_pktsz, pkt, pktsz)) {
>
> ... because eth_pad_short_frame() update it?

Thanks for the review.

The results would be the same, since eth_pad_short_frame() sets
min_pktsz, if at all, to ETH_ZLEN, the same value as the initializer.

I have no objection to re-initializing min_pktsz for each packet,
however, if only to reduce the risk of a bug being introduced if this
behavior of eth_pad_short_frame() were ever to be changed.

Would you like me to post a revised patch?

[PATCH v2] net/vmnet: Pad short Ethernet frames

Posted by William Hooper 3 months, 1 week ago

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 and Philippe Mathieu-Daudé for
reviewing an earlier version.

Signed-off-by: William Hooper <wsh@wshooper.org>
Resolves: https://gitlab.com/qemu-project/qemu/-/issues/2058
---
 net/vmnet-common.m | 22 +++++++++++++++++++---
 1 file changed, 19 insertions(+), 3 deletions(-)

diff --git a/net/vmnet-common.m b/net/vmnet-common.m
index 30c4e53c13..bce1cc590d 100644
--- a/net/vmnet-common.m
+++ b/net/vmnet-common.m
@@ -18,6 +18,7 @@
 #include "qemu/error-report.h"
 #include "qapi/error.h"
 #include "sysemu/runstate.h"
+#include "net/eth.h"
 
 #include <vmnet/vmnet.h>
 #include <dispatch/dispatch.h>
@@ -147,10 +148,25 @@ 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;
+
     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;
+            }
+        }
+
+        ssize_t size = qemu_send_packet_async(&s->nc, pkt, pktsz,
                                       vmnet_send_completed);
 
         if (size == 0) {
-- 
2.37.1

Ping: [PATCH v2] net/vmnet: Pad short Ethernet frames

Posted by William Hooper 1 month, 1 week ago

On Sat, Aug 17, 2024 at 11:33 PM William Hooper <wsh@wshooper.org> wrote:
> 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 and Philippe Mathieu-Daudé for
> reviewing an earlier version.
>
> Signed-off-by: William Hooper <wsh@wshooper.org>
> Resolves: https://gitlab.com/qemu-project/qemu/-/issues/2058
> ---
>  net/vmnet-common.m | 22 +++++++++++++++++++---
>  1 file changed, 19 insertions(+), 3 deletions(-)
>
> diff --git a/net/vmnet-common.m b/net/vmnet-common.m
> index 30c4e53c13..bce1cc590d 100644
> --- a/net/vmnet-common.m
> +++ b/net/vmnet-common.m
> @@ -18,6 +18,7 @@
>  #include "qemu/error-report.h"
>  #include "qapi/error.h"
>  #include "sysemu/runstate.h"
> +#include "net/eth.h"
>
>  #include <vmnet/vmnet.h>
>  #include <dispatch/dispatch.h>
> @@ -147,10 +148,25 @@ 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;
> +
>      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;
> +            }
> +        }
> +
> +        ssize_t size = qemu_send_packet_async(&s->nc, pkt, pktsz,
>                                        vmnet_send_completed);
>
>          if (size == 0) {
> --
> 2.37.1

Ping?

Re: Ping: [PATCH v2] net/vmnet: Pad short Ethernet frames

Posted by Phil Dennis-Jordan 3 weeks, 6 days ago

On Sun, 20 Oct 2024 at 05:17, William Hooper <wsh@wshooper.org> wrote:
>
> On Sat, Aug 17, 2024 at 11:33 PM William Hooper <wsh@wshooper.org> wrote:
> > 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 and Philippe Mathieu-Daudé for
> > reviewing an earlier version.
> >
> > Signed-off-by: William Hooper <wsh@wshooper.org>
> > Resolves: https://gitlab.com/qemu-project/qemu/-/issues/2058
> > ---
> >  net/vmnet-common.m | 22 +++++++++++++++++++---
> >  1 file changed, 19 insertions(+), 3 deletions(-)
> >
> > diff --git a/net/vmnet-common.m b/net/vmnet-common.m
> > index 30c4e53c13..bce1cc590d 100644
> > --- a/net/vmnet-common.m
> > +++ b/net/vmnet-common.m
> > @@ -18,6 +18,7 @@
> >  #include "qemu/error-report.h"
> >  #include "qapi/error.h"
> >  #include "sysemu/runstate.h"
> > +#include "net/eth.h"
> >
> >  #include <vmnet/vmnet.h>
> >  #include <dispatch/dispatch.h>
> > @@ -147,10 +148,25 @@ 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;
> > +
> >      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;
> > +            }
> > +        }
> > +
> > +        ssize_t size = qemu_send_packet_async(&s->nc, pkt, pktsz,
> >                                        vmnet_send_completed);

Nit: Move the declaration of 'size' up to the function header with the
rest of the variables for consistency.

Apart from that:
Reviewed-by: Phil Dennis-Jordan <phil@philjordan.eu>


> >          if (size == 0) {
> > --
> > 2.37.1
>
> Ping?
>

[PATCH v3] net/vmnet: Pad short Ethernet frames

Posted by William Hooper 3 weeks, 2 days ago

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>
---
 net/vmnet-common.m | 23 ++++++++++++++++++++---
 1 file changed, 20 insertions(+), 3 deletions(-)

diff --git a/net/vmnet-common.m b/net/vmnet-common.m
index 30c4e53c13..4b7e330c05 100644
--- a/net/vmnet-common.m
+++ b/net/vmnet-common.m
@@ -18,6 +18,7 @@
 #include "qemu/error-report.h"
 #include "qapi/error.h"
 #include "sysemu/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) {

Ping: [PATCH v3] net/vmnet: Pad short Ethernet frames

Posted by William Hooper 1 week, 2 days ago

On Sat, Nov 2, 2024 at 1:56 PM William Hooper <wsh@wshooper.org> wrote:
> 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>
> ---
>  net/vmnet-common.m | 23 ++++++++++++++++++++---
>  1 file changed, 20 insertions(+), 3 deletions(-)
>
> diff --git a/net/vmnet-common.m b/net/vmnet-common.m
> index 30c4e53c13..4b7e330c05 100644
> --- a/net/vmnet-common.m
> +++ b/net/vmnet-common.m
> @@ -18,6 +18,7 @@
>  #include "qemu/error-report.h"
>  #include "qapi/error.h"
>  #include "sysemu/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) {

Ping?

https://patchew.org/QEMU/20241102205653.30476-1-wsh@wshooper.org/

Re: [PATCH] net/vmnet: Pad short Ethernet frames

Posted by Bin Meng 10 months, 3 weeks ago

On Sun, Jan 7, 2024 at 7:19 AM William Hooper <wsh@wshooper.org> wrote:
>
> 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.
>
> Resolves: https://gitlab.com/qemu-project/qemu/-/issues/2058
> Signed-off-by: William Hooper <wsh@wshooper.org>
> ---
>  net/vmnet-common.m | 20 +++++++++++++++++---
>  1 file changed, 17 insertions(+), 3 deletions(-)
>

Reviewed-by: Bin Meng <bmeng.cn@gmail.com>