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Re: [Qemu-devel] [PATCH] give some useful error messages when tap open f
From: |
Michael Tokarev |
Subject: |
Re: [Qemu-devel] [PATCH] give some useful error messages when tap open fails |
Date: |
Fri, 23 Apr 2010 16:08:02 +0400 |
User-agent: |
Mozilla-Thunderbird 2.0.0.22 (X11/20090706) |
Markus Armbruster wrote:
> Michael Tokarev <address@hidden> writes:
>
>> In net/tap-linux.c, when manipulation of /dev/net/tun fails, it prints
>> (with fprintf) something like this:
>>
>> warning: could not open /dev/net/tun: no virtual network emulation
>>
>> this has 2 issues:
>> 1) it is not a warning really, it's a fatal error (kvm exits after that),
>> 2) there's no indication as of what's actually wrong: printing errno there
>> is helpful.
>>
>> The patch below removes the "warning" prefix, uses %m (since it's linux,
>> %m is available as format modifier), and changes fprintf() to qemu_error().
>> Now it prints something like this instead:
>>
>> could not configure /dev/net/tun: Device or resource busy
>>
>> (there are 2 messages like that in the same function)
>>
>> This fixes Debian bug #578154, see
>> http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=578154
>>
[]
> This might apply to the stable branch (I haven't tried), but I don't
> think it works on master. There, it should look like this (untested):
>
> + error_report("could not open /dev/net/tun: %m");
Yes, the routine name changed in git compared with 0.12. Here goes
the version for current master, which is also a bit more elegant
(I hope anyway). Thanks!
(Still with my Signed-Off-By, if needed:
Signed-Off-By: Michael Tokarev <address@hidden>
)
diff --git a/net/tap-linux.c b/net/tap-linux.c
index 03b8301..6e96607 100644
--- a/net/tap-linux.c
+++ b/net/tap-linux.c
@@ -33,14 +33,15 @@
#include "qemu-common.h"
#include "qemu-error.h"
+#define PATH_NET_TUN "/dev/net/tun"
+
int tap_open(char *ifname, int ifname_size, int *vnet_hdr, int
vnet_hdr_required)
{
struct ifreq ifr;
int fd, ret;
- TFR(fd = open("/dev/net/tun", O_RDWR));
+ TFR(fd = open(PATH_NET_TUN, O_RDWR));
if (fd < 0) {
- fprintf(stderr, "warning: could not open /dev/net/tun: no virtual
network emulation\n");
+ error_report("could not open %s: %m", PATH_NET_TUN);
return -1;
}
memset(&ifr, 0, sizeof(ifr));
@@ -71,7 +73,8 @@ int tap_open(char *ifname, int ifname_size, int *vnet_hdr,
int vnet_hdr_required
pstrcpy(ifr.ifr_name, IFNAMSIZ, "tap%d");
ret = ioctl(fd, TUNSETIFF, (void *) &ifr);
if (ret != 0) {
- fprintf(stderr, "warning: could not configure /dev/net/tun: no virtual
network emulation\n");
+ error_report("could not configure %s (%s): %m", PATH_NET_TUN,
ifr.ifr_name);
close(fd);
return -1;
}