From: Nadav Har'El <[email protected]>
Committer: Nadav Har'El <[email protected]>
Branch: master
SIOCGIFFLAGS ioctl: remove BSD-specific bits
The SIOCGIFFLAGS ioctl returns a set of flags for a network interface.
Many of the classic bits there, like IFF_UP and IFF_LOOPBACK, are the same
in our internal implementation (BSD-based) and desired output (Linux),
but not all of them are the same. We already had a function to convert
the internal bitmask into a Linux bitmask, but it was incomplete.
Of particular importance is BSD's IFF_SIMPLEX flag, which does not exist
on Linux, and is set by OSv's Xen network driver. As we failed to clear
this flag, clients thought they were seeing Linux's IFF_SLAVE (which is
at the same bit position, 0x800). In particular OpenMPI did not like
seeing this flag, and refused to use this network interface.
Fixes #862
Signed-off-by: Nadav Har'El <[email protected]>
Message-Id: <[email protected]>
---
diff --git a/bsd/sys/compat/linux/linux_ioctl.cc
b/bsd/sys/compat/linux/linux_ioctl.cc
--- a/bsd/sys/compat/linux/linux_ioctl.cc
+++ b/bsd/sys/compat/linux/linux_ioctl.cc
@@ -143,26 +143,27 @@ linux_ifconf(struct bsd_ifconf *ifc_p)
return (0);
}
+// While many of the traditional bits returned by SIOCGIFFLAGS are the same
+// on BSD and Linux, some of the newer ones have different location, or
+// different meaning for the same bit location. So we need to convert the
+// BSD bits which we store internally to the Linux bits applications expect
+// us to return.
static void
linux_gifflags(struct ifnet *ifp, struct l_ifreq *ifr)
{
l_short flags;
+ // This assignment drops all the flags beyond the 16th bit.
+ // None of them have a Linux equivalent.
flags = (ifp->if_flags | ifp->if_drv_flags);
- /* These flags have no Linux equivalent
- *
- * Notes:
- * - We do show IFF_SMART|IFF_DRV_OACTIVE|IFF_SIMPLEX
- * - IFF_LINK0 has a value of 0x1000 which conflics with the
Linux
- * IFF_MULTICAST value.
- */
- flags &= ~(IFF_LINK0|IFF_LINK1|IFF_LINK2);
+ // These flags have no Linux equivalent:
+ flags &= ~(IFF_SMART|IFF_DRV_OACTIVE|IFF_SIMPLEX|IFF_LINK0|IFF_LINK1|
IFF_LINK2);
/* Linux' multicast flag is in a different bit */
if (flags & IFF_MULTICAST) {
flags &= ~IFF_MULTICAST;
flags |= 0x1000;
}
- ifr->ifr_flags = flags ;
+ ifr->ifr_flags = flags;
}
#define ARPHRD_ETHER 1
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