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Work around vfs/inet/eth race by avoiding non-blocking ioctl in dhcpd

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This commit is contained in:
Erik van der Kouwe 2010-06-17 12:14:33 +00:00
parent 6312d7238b
commit d59c49aecb
1 changed files with 14 additions and 3 deletions
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17
commands/dhcpd/devices.c
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@ -10,6 +10,7 @@
#include <errno.h>
#include <string.h>
#include <limits.h>
#include <signal.h>
#include <time.h>
#include <sys/ioctl.h>
#include <sys/asynchio.h>
@ -92,6 +93,11 @@ void closefd(fd_t *fdp)
}
}
static void timeout(int signum)
{
/* nothing to do, ioctl will be aborted automatically */
}
int opendev(network_t *np, fdtype_t fdtype, int compete)
{
/* Make sure that a network has the proper device open and configured.
@ -169,14 +175,19 @@ int opendev(network_t *np, fdtype_t fdtype, int compete)
switch (fdtype) {
case FT_ETHERNET:
/* Set NONBLOCK to avoid waiting for a device driver to become ready */
fcntl(np->fdp->fd, F_SETFL, fcntl(np->fdp->fd, F_GETFL) | O_NONBLOCK);
/* Cannot use NWIOGETHSTAT in non-blocking mode due to a race between
* the reply from the ethernet driver and the cancel message from VFS
* for reaching inet. Hence, a signal is used to interrupt NWIOGETHSTAT
* in case the driver isn't ready yet.
*/
if (signal(SIGALRM, timeout) == SIG_ERR) fatal("signal(SIGALRM)");
if (alarm(1) < 0) fatal("alarm(1)");
if (ioctl(np->fdp->fd, NWIOGETHSTAT, &ethstat) < 0) {
/* Not an Ethernet. */
close(fdp->fd);
return 0;
}
fcntl(np->fdp->fd, F_SETFL, fcntl(np->fdp->fd, F_GETFL) & ~O_NONBLOCK);
if (alarm(0) < 0) fatal("alarm(0)");
np->eth= ethstat.nwes_addr;
ethopt.nweo_flags= NWEO_COPY | NWEO_EN_LOC | NWEO_EN_BROAD
| NWEO_REMANY | NWEO_TYPEANY | NWEO_RWDATALL;