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give some useful error messages when tap open

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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

Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
This commit is contained in:
Michael Tokarev 2010-06-02 14:33:01 -03:00 committed by Anthony Liguori
parent 49b586a922
commit 91ca60e012
1 changed files with 5 additions and 3 deletions
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8
net/tap-linux.c
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@ -33,14 +33,16 @@
#include "qemu-common.h" #include "qemu-common.h"
#include "qemu-error.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) int tap_open(char *ifname, int ifname_size, int *vnet_hdr, int vnet_hdr_required)
{ {
struct ifreq ifr; struct ifreq ifr;
int fd, ret; int fd, ret;
TFR(fd = open("/dev/net/tun", O_RDWR)); TFR(fd = open(PATH_NET_TUN, O_RDWR));
if (fd < 0) { 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; return -1;
} }
memset(&ifr, 0, sizeof(ifr)); memset(&ifr, 0, sizeof(ifr));
@ -71,7 +73,7 @@ int tap_open(char *ifname, int ifname_size, int *vnet_hdr, int vnet_hdr_required
pstrcpy(ifr.ifr_name, IFNAMSIZ, "tap%d"); pstrcpy(ifr.ifr_name, IFNAMSIZ, "tap%d");
ret = ioctl(fd, TUNSETIFF, (void *) &ifr); ret = ioctl(fd, TUNSETIFF, (void *) &ifr);
if (ret != 0) { 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); close(fd);
return -1; return -1;
} }