Re: [Qemu-devel] [PATCH 1/1] Make qemu-bridge-helper work in macOS and FreeBSD

[Stefan Hajnoczi <stefanha@gmail.com>]

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On Sat, Apr 07, 2018 at 01:12:05AM +0530, Nikhil Balachandra wrote:
> Eventhough macOS does not ship with the if_bridgevar.h header file[2],
> I expect the API to remain stable as this header file is similar to what
> is found in other BSDs. If this patch is decided to be included in the
> qemu, can experienced qemu developers please tell me how to go about
> having this header file in the include path such that it does not require
> manually downloading and copying the file[3]?

QEMU ships Linux headers.  They are synced using this script:
scripts/update-linux-headers.sh

If the macOS header is appropriately licensed, it could be kept under
include/standard-headers/ alongside the other third-party headers that
QEMU ships.

> @@ -310,30 +374,18 @@ int main(int argc, char **argv)
>          goto cleanup;
>      }
>  
> +
>      /* open the tap device */
> -    fd = open("/dev/net/tun", O_RDWR);
> +    memset(&iface, '\0', sizeof(char) * IFNAMSIZ);
> +    int vnet_supported = has_vnet_hdr(fd);

fd is always -1 here, so this patch breaks vnet hdr?

> +    Error *err = NULL;
> +    fd = tap_open(&iface[0], sizeof(iface), &vnet_supported, use_vnet, 0, &err);

tap_open() was not written with setuid programs in mind.  I think this
is a case where code duplication is justified.

It's safer to have the minimal code to open the tap device rather than
calling into QEMU code which may not realize it is running setuid.

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