datapath: stt compatibility for RHEL7

[cascardo/ovs.git] / FAQ.md

diff --git a/FAQ.md b/FAQ.md
index b112dfb..ff9f932 100644 (file)
--- a/FAQ.md
+++ b/FAQ.md
@@ -173,14 +173,23 @@ A: The following table lists the Linux kernel versions against which the
 
    What should I do?
 
-A: If there is a newer version of Open vSwitch, consider building that
-   one, because it may support the kernel that you are building
-   against.  (To find out, consult the table in the previous answer.)
+A: You have the following options:
 
-   Otherwise, use the Linux kernel module supplied with the kernel
-   that you are using.  All versions of Open vSwitch userspace are
-   compatible with all versions of the Open vSwitch kernel module, so
-   this will also work.  See also the following question.
+   - Use the Linux kernel module supplied with the kernel that you are
+     using.  (See also the following FAQ.)
+
+   - If there is a newer released version of Open vSwitch, consider
+     building that one, because it may support the kernel that you are
+     building against.  (To find out, consult the table in the
+     previous FAQ.)
+
+   - The Open vSwitch "master" branch may support the kernel that you
+     are using, so consider building the kernel module from "master".
+
+  All versions of Open vSwitch userspace are compatible with all
+  versions of the Open vSwitch kernel module, so you do not have to
+  use the kernel module from one source along with the userspace
+  programs from the same source.
 
 ### Q: What features are not available in the Open vSwitch kernel datapath that ships as part of the upstream Linux kernel?
 
@@ -207,7 +216,9 @@ A: Support for tunnels was added to the upstream Linux kernel module
 |:--------:|:-------------:
 | GRE      |    3.11
 | VXLAN    |    3.12
+| Geneve   |    3.18
 | LISP     | <not upstream>
+| STT      | <not upstream>
 
    If you are using a version of the kernel that is older than the one
    listed above, it is still possible to use that tunnel protocol. However,
@@ -216,6 +227,14 @@ A: Support for tunnels was added to the upstream Linux kernel module
    persist after doing this, check to make sure that the module that is
    loaded is the one you expect.
 
+### Q: Why are UDP tunnel checksums not computed for VXLAN or Geneve?
+
+A: Generating outer UDP checksums requires kernel support that was not
+   part of the initial implementation of these protocols. If using the
+   upstream Linux Open vSwitch module, you must use kernel 4.0 or
+   newer. The out-of-tree modules from Open vSwitch release 2.4 and later
+   support UDP checksums.
+
 ### Q: What features are not available when using the userspace datapath?
 
 A: Tunnel virtual ports are not supported, as described in the