[PATCH 4.4 25/46] ipv6: fix flow labels when the traffic class is non-0

From	Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Newsgroups	linux.kernel
Subject	[PATCH 4.4 25/46] ipv6: fix flow labels when the traffic class is non-0
Date	2017-06-15 20:40 +0200
Message-ID	<tSHQv-5ZL-43@gated-at.bofh.it> (permalink)
References	<tSHdL-5vC-7@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Dimitris Michailidis <dmichail@google.com>


[ Upstream commit 90427ef5d2a4b9a24079889bf16afdcdaebc4240 ]

ip6_make_flowlabel() determines the flow label for IPv6 packets. It's
supposed to be passed a flow label, which it returns as is if non-0 and
in some other cases, otherwise it calculates a new value.

The problem is callers often pass a flowi6.flowlabel, which may also
contain traffic class bits. If the traffic class is non-0
ip6_make_flowlabel() mistakes the non-0 it gets as a flow label and
returns the whole thing. Thus it can return a 'flow label' longer than
20b and the low 20b of that is typically 0 resulting in packets with 0
label. Moreover, different packets of a flow may be labeled differently.
For a TCP flow with ECN non-payload and payload packets get different
labels as exemplified by this pair of consecutive packets:

(pure ACK)
Internet Protocol Version 6, Src: 2002:af5:11a3::, Dst: 2002:af5:11a2::
    0110 .... = Version: 6
    .... 0000 0000 .... .... .... .... .... = Traffic Class: 0x00 (DSCP: CS0, ECN: Not-ECT)
        .... 0000 00.. .... .... .... .... .... = Differentiated Services Codepoint: Default (0)
        .... .... ..00 .... .... .... .... .... = Explicit Congestion Notification: Not ECN-Capable Transport (0)
    .... .... .... 0001 1100 1110 0100 1001 = Flow Label: 0x1ce49
    Payload Length: 32
    Next Header: TCP (6)

(payload)
Internet Protocol Version 6, Src: 2002:af5:11a3::, Dst: 2002:af5:11a2::
    0110 .... = Version: 6
    .... 0000 0010 .... .... .... .... .... = Traffic Class: 0x02 (DSCP: CS0, ECN: ECT(0))
        .... 0000 00.. .... .... .... .... .... = Differentiated Services Codepoint: Default (0)
        .... .... ..10 .... .... .... .... .... = Explicit Congestion Notification: ECN-Capable Transport codepoint '10' (2)
    .... .... .... 0000 0000 0000 0000 0000 = Flow Label: 0x00000
    Payload Length: 688
    Next Header: TCP (6)

This patch allows ip6_make_flowlabel() to be passed more than just a
flow label and has it extract the part it really wants. This was simpler
than modifying the callers. With this patch packets like the above become

Internet Protocol Version 6, Src: 2002:af5:11a3::, Dst: 2002:af5:11a2::
    0110 .... = Version: 6
    .... 0000 0000 .... .... .... .... .... = Traffic Class: 0x00 (DSCP: CS0, ECN: Not-ECT)
        .... 0000 00.. .... .... .... .... .... = Differentiated Services Codepoint: Default (0)
        .... .... ..00 .... .... .... .... .... = Explicit Congestion Notification: Not ECN-Capable Transport (0)
    .... .... .... 1010 1111 1010 0101 1110 = Flow Label: 0xafa5e
    Payload Length: 32
    Next Header: TCP (6)

Internet Protocol Version 6, Src: 2002:af5:11a3::, Dst: 2002:af5:11a2::
    0110 .... = Version: 6
    .... 0000 0010 .... .... .... .... .... = Traffic Class: 0x02 (DSCP: CS0, ECN: ECT(0))
        .... 0000 00.. .... .... .... .... .... = Differentiated Services Codepoint: Default (0)
        .... .... ..10 .... .... .... .... .... = Explicit Congestion Notification: ECN-Capable Transport codepoint '10' (2)
    .... .... .... 1010 1111 1010 0101 1110 = Flow Label: 0xafa5e
    Payload Length: 688
    Next Header: TCP (6)

Signed-off-by: Dimitris Michailidis <dmichail@google.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <alexander.levin@verizon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 include/net/ipv6.h |    5 +++++
 1 file changed, 5 insertions(+)

--- a/include/net/ipv6.h
+++ b/include/net/ipv6.h
@@ -744,6 +744,11 @@ static inline __be32 ip6_make_flowlabel(
 {
 	u32 hash;
 
+	/* @flowlabel may include more than a flow label, eg, the traffic class.
+	 * Here we want only the flow label value.
+	 */
+	flowlabel &= IPV6_FLOWLABEL_MASK;
+
 	if (flowlabel ||
 	    net->ipv6.sysctl.auto_flowlabels == IP6_AUTO_FLOW_LABEL_OFF ||
 	    (!autolabel &&

Thread

[PATCH 4.4 00/46] 4.4.73-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-15 20:00 +0200
  [PATCH 4.4 21/46] ethtool: do not vzalloc(0) on registers dump Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-15 20:00 +0200
  [PATCH 4.4 27/46] drm/nouveau/fence/g84-: protect against concurrent access to semaphore buffers Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-15 20:00 +0200
  [PATCH 4.4 33/46] drm/nouveau: Dont enabling polling twice on runtime resume Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-15 20:00 +0200
  [PATCH 4.4 09/46] ipv6: Inhibit IPv4-mapped src address on the wire. Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-15 20:00 +0200
  [PATCH 4.4 32/46] parisc, parport_gsc: Fixes for printk continuation lines Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-15 20:00 +0200
  [PATCH 4.4 45/46] s390/kvm: do not rely on the ILC on kvm host protection fauls Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-15 20:00 +0200
  [PATCH 4.4 17/46] PM / runtime: Avoid false-positive warnings from might_sleep_if() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-15 20:00 +0200
  [PATCH 4.4 37/46] r8152: re-schedule napi for tx Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-15 20:00 +0200
  [PATCH 4.4 22/46] fscache: Fix dead object requeue Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-15 20:00 +0200
  [PATCH 4.4 28/46] net/mlx4_core: Avoid command timeouts during VF driver device shutdown Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-15 20:00 +0200
  [PATCH 4.4 44/46] xtensa: dont use linux IRQ #0 Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-15 20:30 +0200
  [PATCH 4.4 41/46] romfs: use different way to generate fsid for BLOCK or MTD Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-15 20:30 +0200
  [PATCH 4.4 46/46] sparc64: make string buffers large enough Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-15 20:30 +0200
  [PATCH 4.4 38/46] r8152: fix rtl8152_post_reset function Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-15 20:30 +0200
  [PATCH 4.4 42/46] proc: add a schedule point in proc_pid_readdir() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-15 20:30 +0200
  [PATCH 4.4 39/46] r8152: avoid start_xmit to schedule napi when napi is disabled Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-15 20:30 +0200
  [PATCH 4.4 31/46] net: adaptec: starfire: add checks for dma mapping errors Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-15 20:40 +0200
  [PATCH 4.4 24/46] FS-Cache: Initialise stores_lock in netfs cookie Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-15 20:40 +0200
  [PATCH 4.4 30/46] pinctrl: berlin-bg4ct: fix the value for "sd1a" of pin SCRD0_CRD_PRES Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-15 20:40 +0200
  [PATCH 4.4 11/46] NET: mkiss: Fix panic Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-15 20:40 +0200
  [PATCH 4.4 04/46] staging: rtl8192e: rtl92e_fill_tx_desc fix write to mapped out memory. Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-15 20:40 +0200
  [PATCH 4.4 07/46] net: xilinx_emaclite: fix receive buffer overflow Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-15 20:40 +0200
  [PATCH 4.4 08/46] ipv6: Handle IPv4-mapped src to in6addr_any dst. Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-15 20:40 +0200
  [PATCH 4.4 18/46] jump label: pass kbuild_cflags when checking for asm goto support Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-15 20:40 +0200
  [PATCH 4.4 29/46] gianfar: synchronize DMA API usage by free_skb_rx_queue w/ gfar_new_page Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-15 20:40 +0200
  [PATCH 4.4 12/46] net: hns: Fix the device being used for dma mapping during TX Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-15 20:40 +0200
  [PATCH 4.4 35/46] ravb: unmap descriptors when freeing rings Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-15 20:40 +0200
  [PATCH 4.4 03/46] ARM: dts: imx6dl: Fix the VDD_ARM_CAP voltage for 396MHz operation Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-15 20:40 +0200
  [PATCH 4.4 23/46] fscache: Clear outstanding writes when disabling a cookie Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-15 20:40 +0200
  [PATCH 4.4 15/46] i2c: piix4: Fix request_region size Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-15 20:40 +0200
  [PATCH 4.4 10/46] NET: Fix /proc/net/arp for AX.25 Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-15 20:40 +0200
  [PATCH 4.4 25/46] ipv6: fix flow labels when the traffic class is non-0 Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-15 20:40 +0200
  [PATCH 4.4 36/46] nfs: Fix "Dont increment lock sequence ID after NFS4ERR_MOVED" Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-15 20:40 +0200
  [PATCH 4.4 34/46] drm/ast: Fixed system hanged if disable P2A Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-15 20:40 +0200
  [PATCH 4.4 26/46] drm/nouveau: prevent userspace from deleting client object Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-15 20:40 +0200
  [PATCH 4.4 05/46] Call echo service immediately after socket reconnect Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-15 20:40 +0200
  [PATCH 4.4 40/46] sctp: sctp_addr_id2transport should verify the addr before looking up assoc Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-15 20:40 +0200
  [PATCH 4.4 20/46] log2: make order_base_2() behave correctly on const input value zero Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-15 20:40 +0200
  Re: [PATCH 4.4 00/46] 4.4.73-stable review Shuah Khan <shuahkh@osg.samsung.com> - 2017-06-16 00:30 +0200
  Re: [PATCH 4.4 00/46] 4.4.73-stable review Guenter Roeck <linux@roeck-us.net> - 2017-06-16 02:40 +0200

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