Inline IPSEC offload moves almost whole IPSEC processing from the
CPU/MCU and possibly crypto accelerator, to the network card.
The transmitted packet content is not touched by CPU during TX
operations, kernel only does the required policy and security
association lookups to find out that given flow is offloaded, and then
packet is transmitted as plain text to the card. For driver convenience,
a metadata is attached to the packet identifying SA which must process
the packet. Card does encryption of the payload, padding, calculates
authentication, and does the reformat according to the policy.
Similarly, on receive, card does the decapsulation, decryption, and
authentification. Kernel receives the identifier of SA that was
used to process the packet, together with the plain-text packet.
Overall, payload octets are only read or written by card DMA engine,
removing a lot of memory subsystem overhead, and saving CPU time because
IPSEC algos calculations are avoided.
If driver declares support for inline IPSEC offload (with the
IFCAP2_IPSEC_OFFLOAD capability set and registering method table struct
if_ipsec_accel_methods), kernel offers the SPD and SAD to driver.
Driver decides which policies and SAs can be offloaded based on
hardware capacity, and acks/nacks each SA for given interface to
kernel. Kernel needs to keep this information to make a decision to
skip software processing on TX, and to assume processing already done
on RX. This shadow SPD/SAD database of offloads is rooted from
policies (struct secpolicy accel_ifps, struct ifp_handle_sp) and SAs
(struct secasvar accel_ipfs, struct ifp_handle_sav).
Some extensions to the PF_KEY socket allow to limit interfaces for
which given SP/SA could be offloaded (proposed for offload). Also,
additional statistics extensions allow to observe allocation/octet/use
counters for specific SA.
Since SPs and SAs are typically instantiated in non-sleepable context,
while offloading them into card is expected to require costly async
manipulations of the card state, calls to the driver for offload and
termination are executed in the threaded taskqueue. It also solves
the issue of allocating resources needed for the offload database.
Neither ipf_handle_sp nor ipf_handle_sav do not add reference to the
owning SP/SA, the offload must be terminated before last reference is
dropped. ipsec_accel only adds transient references to ensure safe
pointer ownership by taskqueue.
Maintaining the SA counters for hardware-accelerated packets is the
duty of the driver. The helper ipsec_accel_drv_sa_lifetime_update()
is provided to hide accel infrastructure from drivers which would use
expected callout to query hardware periodically for updates.
Reviewed by: rscheff (transport, stack integration), np
Sponsored by: NVIDIA networking
Differential revision: https://reviews.freebsd.org/D44219
PCB SP cache acquires extra reference, when SP is stored in the cache.
Release this reference when PCB is destroyed in ipsec_delete_pcbpolicy().
In ipsec_copy_pcbpolicy() release reference to SP in case if sp_in or
sp_out are not NULL.
Reported by: Slawa Olhovchenkov <slw at zxy spb ru>
MFC after: 1 week
Small summary
-------------
o Almost all IPsec releated code was moved into sys/netipsec.
o New kernel modules added: ipsec.ko and tcpmd5.ko. New kernel
option IPSEC_SUPPORT added. It enables support for loading
and unloading of ipsec.ko and tcpmd5.ko kernel modules.
o IPSEC_NAT_T option was removed. Now NAT-T support is enabled by
default. The UDP_ENCAP_ESPINUDP_NON_IKE encapsulation type
support was removed. Added TCP/UDP checksum handling for
inbound packets that were decapsulated by transport mode SAs.
setkey(8) modified to show run-time NAT-T configuration of SA.
o New network pseudo interface if_ipsec(4) added. For now it is
build as part of ipsec.ko module (or with IPSEC kernel).
It implements IPsec virtual tunnels to create route-based VPNs.
o The network stack now invokes IPsec functions using special
methods. The only one header file <netipsec/ipsec_support.h>
should be included to declare all the needed things to work
with IPsec.
o All IPsec protocols handlers (ESP/AH/IPCOMP protosw) were removed.
Now these protocols are handled directly via IPsec methods.
o TCP_SIGNATURE support was reworked to be more close to RFC.
o PF_KEY SADB was reworked:
- now all security associations stored in the single SPI namespace,
and all SAs MUST have unique SPI.
- several hash tables added to speed up lookups in SADB.
- SADB now uses rmlock to protect access, and concurrent threads
can do SA lookups in the same time.
- many PF_KEY message handlers were reworked to reflect changes
in SADB.
- SADB_UPDATE message was extended to support new PF_KEY headers:
SADB_X_EXT_NEW_ADDRESS_SRC and SADB_X_EXT_NEW_ADDRESS_DST. They
can be used by IKE daemon to change SA addresses.
o ipsecrequest and secpolicy structures were cardinally changed to
avoid locking protection for ipsecrequest. Now we support
only limited number (4) of bundled SAs, but they are supported
for both INET and INET6.
o INPCB security policy cache was introduced. Each PCB now caches
used security policies to avoid SP lookup for each packet.
o For inbound security policies added the mode, when the kernel does
check for full history of applied IPsec transforms.
o References counting rules for security policies and security
associations were changed. The proper SA locking added into xform
code.
o xform code was also changed. Now it is possible to unregister xforms.
tdb_xxx structures were changed and renamed to reflect changes in
SADB/SPDB, and changed rules for locking and refcounting.
Reviewed by: gnn, wblock
Obtained from: Yandex LLC
Relnotes: yes
Sponsored by: Yandex LLC
Differential Revision: https://reviews.freebsd.org/D9352
