[PATCH iproute2-next v3] tc/skbmod: Introduce SKBMOD_F_ECN option
From: Peilin Ye <hidden>
Date: 2021-08-04 18:15:38
Subsystem:
the rest · Maintainer:
Linus Torvalds
From: Peilin Ye <redacted>
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 <redacted>
Signed-off-by: Peilin Ye <redacted>
---
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