seg6: man: ip-link.8: add description of NEXT-C-SID flavor for SRv6 End.X behavior

This patch extends the manpage by providing the description of NEXT-C-SID
support for the SRv6 End.X behavior as defined in RFC 8986 [1].

The code/logic required to handle the "flavors" framework has already been
merged into iproute2 by commit:
    04a6b456bf74 ("seg6: add support for flavors in SRv6 End* behaviors").

Some examples:
ip -6 route add 2001:db8::1 encap seg6local action End.X nh6 fc00::1 flavors next-csid dev eth0

Standard Output:
ip -6 route show 2001:db8::1
2001:db8::1  encap seg6local action End.X nh6 fc00::1 flavors next-csid lblen 32 nflen 16 dev eth0 metric 1024 pref medium

JSON Output:
ip -6 -j -p route show 2001:db8::1
[ {
	"dst": "2001:db8::1",
	"encap": "seg6local",
        "action": "End.X",
        "nh6": "fc00::1",
        "flavors": [ "next-csid" ],
        "lblen": 32,
        "nflen": 16,
	"dev": "eth0",
	"metric": 1024,
	"flags": [ ],
	"pref": "medium"
} ]

[1] - https://datatracker.ietf.org/doc/html/rfc8986

Signed-off-by: Paolo Lungaroni <paolo.lungaroni@uniroma2.it>
Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>

diff --git a/man/man8/ip-route.8.in b/man/man8/ip-route.8.in
index 76151689bcb2104378735e833f2d48847bc0f55c..7a97d7447c6de1470eeb4e205d44cb53c24ddc82 100644 (file)
--- a/man/man8/ip-route.8.in
+++ b/man/man8/ip-route.8.in
@@ -866,10 +866,16 @@ See \fBFlavors parameters\fR section.
 
 .B End.X nh6
 .I NEXTHOP
+.RB [ " flavors "
+.IR FLAVORS " ] "
 - Regular SRv6 processing as intermediate segment endpoint.
 Additionally, forward processed packets to given next-hop.
 This action only accepts packets with a non-zero Segments Left
-value. Other matching packets are dropped.
+value. Other matching packets are dropped. The presence of flavors
+can change the regular processing of an End.X behavior according to
+the user-provided Flavor operations and information carried in the packet.
+See \fBFlavors parameters\fR section.
+
 
 .B End.DX6 nh6
 .I NEXTHOP
@@ -977,7 +983,7 @@ subset of the existing behaviors.
 removes (i.e. pops) the SRH from the IPv6 header.
 The PSP operation takes place only at a penultimate SR Segment Endpoint node
 (e.g., the Segment Left must be one) and does not happen at non-penultimate
-endpoint nodes.
+endpoint nodes. This flavor is currently only supported by End behavior.
 
 .B usp
 - Ultimate Segment Pop of the SRH (not yet supported in kernel)