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Re: [Qemu-devel] [PATCH] net: provide a friendly message when a user pas
From: |
Jason Wang |
Subject: |
Re: [Qemu-devel] [PATCH] net: provide a friendly message when a user passes a bad -net tap, fd=X (v2) |
Date: |
Tue, 12 Oct 2010 02:41:49 -0400 (EDT) |
----- "Anthony Liguori" <address@hidden> wrote:
> A lot of people copy libvirt's command line from ps -ef and then
> wonder why the
> VM isn't working correctly. Let's be kind and tell them what they
> should do
> instead.
>
> Without this patch, if you run with an invalid -net tap,fd=X, the
> guest still
> runs and we poll 100% on a bad file descriptor. With this patch, you
> get:
>
> qemu: -net tap,fd=42: invalid fd= for tap network device. If you're
> copying
> from libvirt, use `virsh dom2xml-to-native' instead
> qemu: -net tap,fd=42: Device 'tap' could not be initialized
>
> Signed-off-by: Anthony Liguori <address@hidden>
> ---
> v1 -> v2
> - Remove garbage from unclean commit (spotted by Alex Graf)
>
> diff --git a/net/tap.c b/net/tap.c
> index 0147dab..45b1fb6 100644
> --- a/net/tap.c
> +++ b/net/tap.c
> @@ -405,6 +405,8 @@ int net_init_tap(QemuOpts *opts, Monitor *mon,
> const char *name, VLANState *vlan
> int fd, vnet_hdr = 0;
>
> if (qemu_opt_get(opts, "fd")) {
> + int flags;
> +
> if (qemu_opt_get(opts, "ifname") ||
> qemu_opt_get(opts, "script") ||
> qemu_opt_get(opts, "downscript") ||
> @@ -418,6 +420,11 @@ int net_init_tap(QemuOpts *opts, Monitor *mon,
> const char *name, VLANState *vlan
> return -1;
> }
>
> + if (fcntl(fd, F_GETFL, &flags) == -1) {
> + error_report("invalid fd= for tap network device. If
> you're copying from libvirt, use `virsh dom2xml-to-native' instead");
> + return -1;
> + }
> +
Maybe we can use TUNGETFEATURES here to verify whether fd is a tap here?
> fcntl(fd, F_SETFL, O_NONBLOCK);
>
> vnet_hdr = tap_probe_vnet_hdr(fd);
> --
> 1.7.0.4
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