XFRM Interface Development Notes
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Development notes for XFRMi
libreswan/pluto design choices
- allow names ipsec0, ipsec1 ... ipsecx.
- Should we allow names other than ipsecXX ?
- initial thought is keep "xfrm interface id" and "xfrm output mark" consistent.
- interface creation is inside pluto.
- create bugzilla entry for Fedora/CentOS kernels? Fedora 28 do not enable
XFRM INTERFACE
Commit cover letter from Steffen 20180612, Merged in 4.19:
https://patchwork.ozlabs.org/cover/928175/ Steffen Klassert June 12, 2018, 7:56 a.m. This patchset introduces new virtual xfrm interfaces. The design of virtual xfrm interfaces interfaces was discussed at the Linux IPsec workshop 2018. This patchset implements these interfaces as the IPsec userspace and kernel developers agreed. The purpose of these interfaces is to overcome the design limitations that the existing VTI devices have. The main limitations that we see with the current VTI are the following: - VTI interfaces are L3 tunnels with configurable endpoints. For xfrm, the tunnel endpoint are already determined by the SA. So the VTI tunnel endpoints must be either the same as on the SA or wildcards. In case VTI tunnel endpoints are same as on the SA, we get a one to one correlation between the SA and the tunnel. So each SA needs its own tunnel interface. On the other hand, we can have only one VTI tunnel with wildcard src/dst tunnel endpoints in the system because the lookup is based on the tunnel endpoints. The existing tunnel lookup won't work with multiple tunnels with wildcard tunnel endpoints. Some usecases require more than on VTI tunnel of this type, for example if somebody has multiple namespaces and every namespace requires such a VTI. - VTI needs separate interfaces for IPv4 and IPv6 tunnels. So when routing to a VTI, we have to know to which address family this traffic class is going to be encapsulated. This is a lmitation because it makes routing more complex and it is not always possible to know what happens behind the VTI, e.g. when the VTI is move to some namespace. - VTI works just with tunnel mode SAs. We need generic interfaces that ensures transfomation, regardless of the xfrm mode and the encapsulated address family. - VTI is configured with a combination GRE keys and xfrm marks. With this we have to deal with some extra cases in the generic tunnel lookup because the GRE keys on the VTI are actually not GRE keys, the GRE keys were just reused for something else. All extensions to the VTI interfaces would require to add even more complexity to the generic tunnel lookup. To overcome this, we started with the following design goal: - It should be possible to tunnel IPv4 and IPv6 through the same interface. - No limitation on xfrm mode (tunnel, transport and beet). - Should be a generic virtual interface that ensures IPsec transformation, no need to know what happens behind the interface. - Interfaces should be configured with a new key that must match a new policy/SA lookup key. - The lookup logic should stay in the xfrm codebase, no need to change or extend generic routing and tunnel lookups. - Should be possible to use IPsec hardware offloads of the underlying interface.
Initial xfrmi kernel commits
- Steffen Klassert's at Linux IPsec 2018, Dresden https://workshop.linux-ipsec.org/2018/slides/xfrm_interfaces.pdf
XFRM OUTPUT Mark extension with mask (Related, required commit)
XFRM output mark is different from XFRMA_MARK. Extention with mask
= Which mark?
Details of tow marks in Linux xfrm. There are two marks XFRMA_MARK and XFRMA_SET_MARK(XFRMA_OUTPUT_MARK)
XFRMA_SET_MARK has the format "mark/[mask]" While XFRMA_MARK
Fedora support
- F29 commit enabled it. However not in F28
- RHEL bugzilla request??