seg6: man: ip-link.8: add SRv6 End PSP flavor description

This patch extends the manpage by providing a brief description of the PSP
flavor for the SRv6 End 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 flavors psp dev eth0

Standard Output:
ip -6 route show 2001:db8::1
2001:db8::1  encap seg6local action End flavors psp 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",
	"flavors": [ "psp" ],
	"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: David Ahern <dsahern@kernel.org>

diff --git a/man/man8/ip-route.8.in b/man/man8/ip-route.8.in
index 194dc780d890e5b37f406ed7f5be9fa7eb35e7ec..c2b00833e50794e6a8092c9553effc1e972c8eb8 100644 (file)
--- a/man/man8/ip-route.8.in
+++ b/man/man8/ip-route.8.in
@@ -963,7 +963,12 @@ subset of the existing behaviors.
 .in -2
 
 .B psp
-- Penultimate Segment Pop of the SRH (not yet supported in kernel)
+- The Penultimate Segment Pop (PSP) copies the last SID from the SID List
+(carried by the outermost SRH) into the IPv6 Destination Address (DA) and
+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.
 
 .B usp
 - Ultimate Segment Pop of the SRH (not yet supported in kernel)
@@ -1359,6 +1364,11 @@ ip -6 route add 2001:db8:1::/64 encap seg6local action End.DT46 vrftable 100 dev
 Adds an IPv6 route with SRv6 decapsulation and forward with lookup in VRF table.
 .RE
 .PP
+ip -6 route add 2001:db8:1::/64 encap seg6local action End flavors psp dev eth0
+.RS 4
+Adds an IPv6 route with SRv6 End behavior with psp flavor enabled.
+.RE
+.PP
 ip -6 route add 2001:db8:1::/64 encap seg6local action End flavors next-csid dev eth0
 .RS 4
 Adds an IPv6 route with SRv6 End behavior with next-csid flavor enabled.