[PATCH iproute2-next v2 0/3] Support pedit of ip6 traffic_class

[PATCH iproute2-next v2 0/3] Support pedit of ip6 traffic_class

[Petr Machata]

The pedit action supports tos (and its synonyms, such as dsfield) for IPv4,
but not the corresponding IPv6 field, traffic_class. Patch #1 of this
series adds this IPv6 support. Patch #2 then adds two related examples to
man page, and patch #3 removes from the man page a claim that the extended
notation is only available for IPv4.

v2:
- Patch #1:
    - Only accept 'traffic_class'.
    - Move the if-branch that matches it to the end of the list.
    - man: Drop the untrue statement that the traffic_class field needs
      to be sandwiched between two 4-bit zeroes.

Petr Machata (3):
  tc: p_ip6: Support pedit of IPv6 dsfield
  man: tc-pedit: Add examples for dsfield and retain
  man: tc-pedit: Drop the claim that pedit ex is only for IPv4

 man/man8/tc-pedit.8 | 31 +++++++++++++++++++++++++++----
 tc/p_ip6.c          | 15 +++++++++++++++
 2 files changed, 42 insertions(+), 4 deletions(-)

-- 
2.20.1

[PATCH iproute2-next v2 1/3] tc: p_ip6: Support pedit of IPv6 dsfield

[Petr Machata]

Support keywords dsfield, traffic_class and tos in the IPv6 context.

Signed-off-by: Petr Machata <petrm@mellanox.com>
---

Notes:
    v2:
    - Only accept 'traffic_class'.
    - Move the if-branch that matches it to the end of the list.
    - man: Drop the untrue statement that the traffic_class field needs
      to be sandwiched between two 4-bit zeroes.

 man/man8/tc-pedit.8 |  6 ++++--
 tc/p_ip6.c          | 15 +++++++++++++++
 2 files changed, 19 insertions(+), 2 deletions(-)

diff --git a/man/man8/tc-pedit.8 b/man/man8/tc-pedit.8
index bbd725c4..3f6baa3d 100644
--- a/man/man8/tc-pedit.8
+++ b/man/man8/tc-pedit.8
@@ -60,8 +60,8 @@ pedit - generic packet editor action
 
 .ti -8
 .IR IP6HDR_FIELD " := { "
-.BR src " | " dst " | " flow_lbl " | " payload_len " | " nexthdr " |"
-.BR hoplimit " }"
+.BR src " | " dst " | " traffic_class " | " flow_lbl " | " payload_len " | "
+.BR nexthdr " | " hoplimit " }"
 
 .ti -8
 .IR TCPHDR_FIELD " := { "
@@ -229,6 +229,8 @@ are:
 .TQ
 .B dst
 .TQ
+.B traffic_class
+.TQ
 .B flow_lbl
 .TQ
 .B payload_len
diff --git a/tc/p_ip6.c b/tc/p_ip6.c
index 7cc7997b..71660c61 100644
--- a/tc/p_ip6.c
+++ b/tc/p_ip6.c
@@ -74,6 +74,21 @@ parse_ip6(int *argc_p, char ***argv_p,
 		res = parse_cmd(&argc, &argv, 1, TU32, RU8, sel, tkey);
 		goto done;
 	}
+	if (strcmp(*argv, "traffic_class") == 0) {
+		NEXT_ARG();
+		tkey->off = 1;
+		res = parse_cmd(&argc, &argv, 1, TU32, RU8, sel, tkey);
+
+		/* Shift the field by 4 bits on success. */
+		if (!res) {
+			int nkeys = sel->sel.nkeys;
+			struct tc_pedit_key *key = &sel->sel.keys[nkeys - 1];
+
+			key->mask = htonl(ntohl(key->mask) << 4 | 0xf);
+			key->val = htonl(ntohl(key->val) << 4);
+		}
+		goto done;
+	}
 
 	return -1;
 
-- 
2.20.1

[PATCH iproute2-next v2 2/3] man: tc-pedit: Add examples for dsfield and retain

[Petr Machata]

Describe a way to update just the DSCP and just the ECN part of the
dsfield. That is useful on its own, but also it shows how retain works.

Signed-off-by: Petr Machata <petrm@mellanox.com>
---
 man/man8/tc-pedit.8 | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/man/man8/tc-pedit.8 b/man/man8/tc-pedit.8
index 3f6baa3d..d2b37ef0 100644
--- a/man/man8/tc-pedit.8
+++ b/man/man8/tc-pedit.8
@@ -369,6 +369,28 @@ tc filter add dev eth0 parent ffff: u32 \\
 	action pedit ex munge tcp dport set 22
 .EE
 .RE
+
+To rewrite just part of a field, use the
+.B retain
+directive. E.g. to overwrite the DSCP part of a dsfield with $DSCP, without
+touching ECN:
+
+.RS
+.EX
+tc filter add dev eth0 ingress flower ... \\
+	action pedit ex munge ip dsfield set $((DSCP << 2)) retain 0xfc
+.EE
+.RE
+
+And vice versa, to set ECN to e.g. 1 without impacting DSCP:
+
+.RS
+.EX
+tc filter add dev eth0 ingress flower ... \\
+	action pedit ex munge ip dsfield set 1 retain 0x3
+.EE
+.RE
+
 .SH SEE ALSO
 .BR tc (8),
 .BR tc-htb (8),
-- 
2.20.1

[PATCH iproute2-next v2 3/3] man: tc-pedit: Drop the claim that pedit ex is only for IPv4

[Petr Machata]

This sentence predates addition of extended pedit for IPv6 packets.

Reported-by: Ido Schimmel <idosch@mellanox.com>
Signed-off-by: Petr Machata <petrm@mellanox.com>
---
 man/man8/tc-pedit.8 | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/man/man8/tc-pedit.8 b/man/man8/tc-pedit.8
index d2b37ef0..376ad4a8 100644
--- a/man/man8/tc-pedit.8
+++ b/man/man8/tc-pedit.8
@@ -90,8 +90,7 @@ action can be used to change arbitrary packet data. The location of data to
 change can either be specified by giving an offset and size as in
 .IR RAW_OP ,
 or for header values by naming the header and field to edit the size is then
-chosen automatically based on the header field size. Currently this is supported
-only for IPv4 headers.
+chosen automatically based on the header field size.
 .SH OPTIONS
 .TP
 .B ex
-- 
2.20.1

Re: [PATCH iproute2-next v2 0/3] Support pedit of ip6 traffic_class

[David Ahern]

On 4/3/20 5:05 PM, Petr Machata wrote:
> The pedit action supports tos (and its synonyms, such as dsfield) for IPv4,
> but not the corresponding IPv6 field, traffic_class. Patch #1 of this
> series adds this IPv6 support. Patch #2 then adds two related examples to
> man page, and patch #3 removes from the man page a claim that the extended
> notation is only available for IPv4.
> 
applied to iproute2-next. Thanks