(1) bpf peer attaches to interface netif0
(2) Packet is received by netif0
(3) ifp->if_bpf pointer is checked and handed off to bpf
(4) bpf peer detaches from netif0 resulting in ifp->if_bpf being
initialized to NULL.
(5) ifp->if_bpf is dereferenced by bpf machinery
(6) Kaboom
This race condition likely explains the various different kernel panics
reported around sending SIGINT to tcpdump or dhclient processes. But really
this race can result in kernel panics anywhere you have frequent bpf attach
and detach operations with high packet per second load.
Summary of changes:
- Remove the bpf interface's "driverp" member
- When we attach bpf interfaces, we now set the ifp->if_bpf member to the
bpf interface structure. Once this is done, ifp->if_bpf should never be
NULL. [1]
- Introduce bpf_peers_present function, an inline operation which will do
a lockless read bpf peer list associated with the interface. It should
be noted that the bpf code will pickup the bpf_interface lock before adding
or removing bpf peers. This should serialize the access to the bpf descriptor
list, removing the race.
- Expose the bpf_if structure in bpf.h so that the bpf_peers_present function
can use it. This also removes the struct bpf_if; hack that was there.
- Adjust all consumers of the raw if_bpf structure to use bpf_peers_present
Now what happens is:
(1) Packet is received by netif0
(2) Check to see if bpf descriptor list is empty
(3) Pickup the bpf interface lock
(4) Hand packet off to process
From the attach/detach side:
(1) Pickup the bpf interface lock
(2) Add/remove from bpf descriptor list
Now that we are storing the bpf interface structure with the ifnet, there is
is no need to walk the bpf interface list to locate the correct bpf interface.
We now simply look up the interface, and initialize the pointer. This has a
nice side effect of changing a bpf interface attach operation from O(N) (where
N is the number of bpf interfaces), to O(1).
[1] From now on, we can no longer check ifp->if_bpf to tell us whether or
not we have any bpf peers that might be interested in receiving packets.
In collaboration with: sam@
MFC after: 1 month
Vararg functions have a different calling convention than regular
functions on amd64. Casting a varag function to a regular one to
match the function pointer declaration will hide the varargs from
the caller and we will end up with an incorrectly setup stack.
Entirely remove the varargs from these functions and change the
functions to match the declaration of the function pointers.
Remove the now unnecessary casts.
Lots of explanations and help from: peter
Reviewed by: peter
PR: amd64/89261
MFC after: 6 days
FreeBSD specific ip_newid() changes NetBSD does not have.
Correct handling of non AF_INET packets passed to bpf [2].
PR: kern/80340[1], NetBSD PRs 29150[1], 30844[2]
Obtained from: NetBSD ip_gre.c rev. 1.34,1.35, if_gre.c rev. 1.56
Submitted by: Gert Doering <gert at greenie.muc.de>[2]
MFC after: 4 days
struct ifnet or the layer 2 common structure it was embedded in have
been replaced with a struct ifnet pointer to be filled by a call to the
new function, if_alloc(). The layer 2 common structure is also allocated
via if_alloc() based on the interface type. It is hung off the new
struct ifnet member, if_l2com.
This change removes the size of these structures from the kernel ABI and
will allow us to better manage them as interfaces come and go.
Other changes of note:
- Struct arpcom is no longer referenced in normal interface code.
Instead the Ethernet address is accessed via the IFP2ENADDR() macro.
To enforce this ac_enaddr has been renamed to _ac_enaddr.
- The second argument to ether_ifattach is now always the mac address
from driver private storage rather than sometimes being ac_enaddr.
Reviewed by: sobomax, sam
- Trailing tab/space cleanup
- Remove spurious spaces between or before tabs
This change avoids touching files that Andre likely has in his working
set for PFIL hooks changes for IPFW/DUMMYNET.
Approved by: re (scottl)
Submitted by: Xin LI <delphij@frontfree.net>
- Add gre_mtx to protect global softc list.
- Hold gre_mtx over various list operations (insert, delete).
- Centralize if_gre interface teardown in gre_destroy(), and call this
from modevent unload and gre_clone_destroy().
- Export gre_mtx to ip_gre.c, which walks the gre list to look up gre
interfaces during encapsulation. Add a wonking comment on how we need
some sort of drain/reference count mechanism to keep gre references
alive while in use and simultaneous destroy.
This commit does not lockdown softc data, which follows in a future
commit.
ifconfig(8) flag since header for version 2 is the same but IP payload
is prepended with additional 4-bytes field.
Inspired by: Roman Synyuk <roman@univ.kiev.ua>
MFC after: 2 weeks
if_gre.c rev.1.41-1.49
o Spell output with two ts.
o Remove assigned-to but not used variable.
o fix grammatical error in a diagnostic message.
o u_short -> u_int16_t.
o gi_len is ip_len, so it has to be network byteorder.
if_gre.h rev.1.11-1.13
o prototype must not have variable name.
o u_short -> u_int16_t.
o Spell address with two d's.
ip_gre.c rev.1.22-1.29
o KNF - return is not a function.
o The "osrc" variable in gre_mobile_input() is only ever set but not
referenced; remove it.
o correct (false) assumptions on mbuf chain. not sure if it really helps, but
anyways, it is necessary to perform m_pullup.
o correct arg to m_pullup (need to count IP header size as well).
o remove redundant adjustment of m->m_pkthdr.len.
o clear m_flags just for safety.
o tabify.
o u_short -> u_int16_t.
MFC after: 2 weeks
a new bpf_mtap2 routine that does the right thing for an mbuf
and a variable-length chunk of data that should be prepended.
o while we're sweeping the drivers, use u_int32_t uniformly when
when prepending the address family (several places were assuming
sizeof(int) was 4)
o return M_ASSERTVALID to BPF_MTAP* now that all stack-allocated
mbufs have been eliminated; this may better be moved to the bpf
routines
Reviewed by: arch@ and several others
drain routines are done by swi_net, which allows for better queue control
at some future point. Packets may also be directly dispatched to a netisr
instead of queued, this may be of interest at some installations, but
currently defaults to off.
Reviewed by: hsu, silby, jayanth, sam
Sponsored by: DARPA, NAI Labs
