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Message-Id: <20210804181516.11921-1-yepeilin.cs@gmail.com>
Date: Wed, 4 Aug 2021 11:15:16 -0700
From: Peilin Ye <yepeilin.cs@...il.com>
To: netdev@...r.kernel.org, David Ahern <dsahern@...il.com>
Cc: Stephen Hemminger <stephen@...workplumber.org>,
Jamal Hadi Salim <jhs@...atatu.com>,
Cong Wang <xiyou.wangcong@...il.com>,
Jiri Pirko <jiri@...nulli.us>,
Cong Wang <cong.wang@...edance.com>,
Peilin Ye <peilin.ye@...edance.com>,
Peilin Ye <yepeilin.cs@...il.com>
Subject: [PATCH iproute2-next v3] tc/skbmod: Introduce SKBMOD_F_ECN option
From: Peilin Ye <peilin.ye@...edance.com>
Recently we added SKBMOD_F_ECN option support to the kernel; support it in
the tc-skbmod(8) front end, and update its man page accordingly.
The 2 least significant bits of the Traffic Class field in IPv4 and IPv6
headers are used to represent different ECN states [1]:
0b00: "Non ECN-Capable Transport", Non-ECT
0b10: "ECN Capable Transport", ECT(0)
0b01: "ECN Capable Transport", ECT(1)
0b11: "Congestion Encountered", CE
This new option, "ecn", marks ECT(0) and ECT(1) IPv{4,6} packets as CE,
which is useful for ECN-based rate limiting. For example:
$ tc filter add dev eth0 parent 1: protocol ip prio 10 \
u32 match ip protocol 1 0xff flowid 1:2 \
action skbmod \
ecn
The updated tc-skbmod SYNOPSIS looks like the following:
tc ... action skbmod { set SETTABLE | swap SWAPPABLE | ecn } ...
Only one of "set", "swap" or "ecn" shall be used in a single tc-skbmod
command. Trying to use more than one of them at a time is considered
undefined behavior; pipe multiple tc-skbmod commands together instead.
"set" and "swap" only affect Ethernet packets, while "ecn" only affects
IP packets.
Depends on kernel patch "net/sched: act_skbmod: Add SKBMOD_F_ECN option
support", as well as iproute2 patch "tc/skbmod: Remove misinformation
about the swap action".
[1] https://en.wikipedia.org/wiki/Explicit_Congestion_Notification
Reviewed-by: Cong Wang <cong.wang@...edance.com>
Signed-off-by: Peilin Ye <peilin.ye@...edance.com>
---
Hi David,
> I just merged main into next. Please fix up this patch and re-send. In
> the future, just ask for a merge in cases like this.
Ah, I see; thanks!
Peilin Ye
Change since v2:
- re-rebased on iproute2-next (David)
man/man8/tc-skbmod.8 | 38 +++++++++++++++++++++++++++++---------
tc/m_skbmod.c | 8 +++++++-
2 files changed, 36 insertions(+), 10 deletions(-)
diff --git a/man/man8/tc-skbmod.8 b/man/man8/tc-skbmod.8
index 76512311b17d..52eaf989e80b 100644
--- a/man/man8/tc-skbmod.8
+++ b/man/man8/tc-skbmod.8
@@ -8,7 +8,8 @@ skbmod - user-friendly packet editor action
.BR tc " ... " "action skbmod " "{ " "set "
.IR SETTABLE " | "
.BI swap " SWAPPABLE"
-.RI " } [ " CONTROL " ] [ "
+.RB " | " ecn
+.RI "} [ " CONTROL " ] [ "
.BI index " INDEX "
]
@@ -37,6 +38,12 @@ action. Instead of having to manually edit 8-, 16-, or 32-bit chunks of an
ethernet header,
.B skbmod
allows complete substitution of supported elements.
+Action must be one of
+.BR set ", " swap " and " ecn "."
+.BR set " and " swap
+only affect Ethernet packets, while
+.B ecn
+only affects IP packets.
.SH OPTIONS
.TP
.BI dmac " DMAC"
@@ -51,6 +58,10 @@ Change the ethertype to the specified value.
.BI mac
Used to swap mac addresses.
.TP
+.B ecn
+Used to mark ECN Capable Transport (ECT) IP packets as Congestion Encountered (CE).
+Does not affect Non ECN-Capable Transport (Non-ECT) packets.
+.TP
.I CONTROL
The following keywords allow to control how the tree of qdisc, classes,
filters and actions is further traversed after this action.
@@ -115,7 +126,7 @@ tc filter add dev eth5 parent 1: protocol ip prio 10 \\
.EE
.RE
-Finally, swap the destination and source mac addresses in the header:
+To swap the destination and source mac addresses in the Ethernet header:
.RS
.EX
@@ -126,13 +137,22 @@ tc filter add dev eth3 parent 1: protocol ip prio 10 \\
.EE
.RE
-However, trying to
-.B set
-and
-.B swap
-in a single
-.B skbmod
-command will cause undefined behavior.
+Finally, to mark the CE codepoint in the IP header for ECN Capable Transport (ECT) packets:
+
+.RS
+.EX
+tc filter add dev eth0 parent 1: protocol ip prio 10 \\
+ u32 match ip protocol 1 0xff flowid 1:2 \\
+ action skbmod \\
+ ecn
+.EE
+.RE
+
+Only one of
+.BR set ", " swap " and " ecn
+shall be used in a single command.
+Trying to use more than one of them in a single command is considered undefined behavior; pipe
+multiple commands together instead.
.SH SEE ALSO
.BR tc (8),
diff --git a/tc/m_skbmod.c b/tc/m_skbmod.c
index 3fe30651a7d8..8d8bac5bc481 100644
--- a/tc/m_skbmod.c
+++ b/tc/m_skbmod.c
@@ -28,7 +28,7 @@
static void skbmod_explain(void)
{
fprintf(stderr,
- "Usage:... skbmod { set <SETTABLE> | swap <SWAPPABLE> } [CONTROL] [index INDEX]\n"
+ "Usage:... skbmod { set <SETTABLE> | swap <SWAPPABLE> | ecn } [CONTROL] [index INDEX]\n"
"where SETTABLE is: [dmac DMAC] [smac SMAC] [etype ETYPE]\n"
"where SWAPPABLE is: \"mac\" to swap mac addresses\n"
"\tDMAC := 6 byte Destination MAC address\n"
@@ -111,6 +111,9 @@ static int parse_skbmod(struct action_util *a, int *argc_p, char ***argv_p,
p.flags |= SKBMOD_F_SMAC;
fprintf(stderr, "src MAC address <%s>\n", saddr);
ok += 1;
+ } else if (matches(*argv, "ecn") == 0) {
+ p.flags |= SKBMOD_F_ECN;
+ ok += 1;
} else if (matches(*argv, "help") == 0) {
skbmod_usage();
} else {
@@ -211,6 +214,9 @@ static int print_skbmod(struct action_util *au, FILE *f, struct rtattr *arg)
if (p->flags & SKBMOD_F_SWAPMAC)
fprintf(f, "swap mac ");
+ if (p->flags & SKBMOD_F_ECN)
+ fprintf(f, "ecn ");
+
fprintf(f, "\n\t index %u ref %d bind %d", p->index, p->refcnt,
p->bindcnt);
if (show_stats) {
--
2.20.1
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