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Vladimir Oltean 1f922d9e37 Revert "net: procfs: add seq_puts() statement for dev_mcast" 
This reverts commit ec18e84554.

It turns out that there are user space programs which got broken by that
change. One example is the "ifstat" program shipped by Debian:
https://packages.debian.org/source/bullseye/ifstat
which, confusingly enough, seems to not have anything in common with the
much more familiar (at least to me) ifstat program from iproute2:
https://git.kernel.org/pub/scm/network/iproute2/iproute2.git/tree/misc/ifstat.c

root@debian:~# ifstat
ifstat: /proc/net/dev: unsupported format.

This change modified the header (first two lines of text) in
/proc/net/dev so that it looks like this:

root@debian:~# cat /proc/net/dev
Interface|                            Receive                                       |                                 Transmit
         |            bytes      packets errs   drop fifo frame compressed multicast|            bytes      packets errs   drop fifo colls carrier compressed
       lo:            97400         1204    0      0    0     0          0         0            97400         1204    0      0    0     0       0          0
    bond0:                0            0    0      0    0     0          0         0                0            0    0      0    0     0       0          0
     sit0:                0            0    0      0    0     0          0         0                0            0    0      0    0     0       0          0
     eno2:          5002206         6651    0      0    0     0          0         0        105518642      1465023    0      0    0     0       0          0
     swp0:           134531         2448    0      0    0     0          0         0         99599598      1464381    0      0    0     0       0          0
     swp1:                0            0    0      0    0     0          0         0                0            0    0      0    0     0       0          0
     swp2:          4867675         4203    0      0    0     0          0         0            58134          631    0      0    0     0       0          0
    sw0p0:                0            0    0      0    0     0          0         0                0            0    0      0    0     0       0          0
    sw0p1:           124739         2448    0   1422    0     0          0         0         93741184      1464369    0      0    0     0       0          0
    sw0p2:                0            0    0      0    0     0          0         0                0            0    0      0    0     0       0          0
    sw2p0:          4850863         4203    0      0    0     0          0         0            54722          619    0      0    0     0       0          0
    sw2p1:                0            0    0      0    0     0          0         0                0            0    0      0    0     0       0          0
    sw2p2:                0            0    0      0    0     0          0         0                0            0    0      0    0     0       0          0
    sw2p3:                0            0    0      0    0     0          0         0                0            0    0      0    0     0       0          0
      br0:            10508          212    0    212    0     0          0       212         61369558       958857    0      0    0     0       0          0

whereas before it looked like this:

root@debian:~# cat /proc/net/dev
Inter-|   Receive                                                |  Transmit
 face |bytes    packets errs drop fifo frame compressed multicast|bytes    packets errs drop fifo colls carrier compressed
    lo:   13160     164    0    0    0     0          0         0    13160     164    0    0    0     0       0          0
 bond0:       0       0    0    0    0     0          0         0        0       0    0    0    0     0       0          0
  sit0:       0       0    0    0    0     0          0         0        0       0    0    0    0     0       0          0
  eno2:   30824     268    0    0    0     0          0         0     3332      37    0    0    0     0       0          0
  swp0:       0       0    0    0    0     0          0         0        0       0    0    0    0     0       0          0
  swp1:       0       0    0    0    0     0          0         0        0       0    0    0    0     0       0          0
  swp2:   30824     268    0    0    0     0          0         0     2428      27    0    0    0     0       0          0
 sw0p0:       0       0    0    0    0     0          0         0        0       0    0    0    0     0       0          0
 sw0p1:       0       0    0    0    0     0          0         0        0       0    0    0    0     0       0          0
 sw0p2:       0       0    0    0    0     0          0         0        0       0    0    0    0     0       0          0
 sw2p0:   29752     268    0    0    0     0          0         0     1564      17    0    0    0     0       0          0
 sw2p1:       0       0    0    0    0     0          0         0        0       0    0    0    0     0       0          0
 sw2p2:       0       0    0    0    0     0          0         0        0       0    0    0    0     0       0          0
 sw2p3:       0       0    0    0    0     0          0         0        0       0    0    0    0     0       0          0

The reason why the ifstat shipped by Debian (v1.1, with a Debian patch
upgrading it to 1.1-8.1 at the time of writing) is broken is because its
"proc" driver/backend parses the header very literally:

main/drivers.c#L825
  if (!data->checked && strncmp(buf, "Inter-|", 7))
    goto badproc;

and there's no way in which the header can be changed such that programs
parsing like that would not get broken.

Even if we fix this ancient and very "lightly" maintained program to
parse the text output of /proc/net/dev in a more sensible way, this
story seems bound to repeat again with other programs, and modifying
them all could cause more trouble than it's worth. On the other hand,
the reverted patch had no other reason than an aesthetic one, so
reverting it is the simplest way out.

I don't know what other distributions would be affected; the fact that
Debian doesn't ship the iproute2 version of the program (a different
code base altogether, which uses netlink and not /proc/net/dev) is
surprising in itself.

Fixes: ec18e84554 ("net: procfs: add seq_puts() statement for dev_mcast")
Link: https://lore.kernel.org/netdev/20211009163511.vayjvtn3rrteglsu@skbuf/
Cc: Yajun Deng <yajun.deng@linux.dev>
Cc: Matthieu Baerts <matthieu.baerts@tessares.net>
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Link: https://lore.kernel.org/r/20211013001909.3164185-1-vladimir.oltean@nxp.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
2021-10-13 17:24:38 -07:00
..
bpf_sk_storage.c net: in_irq() cleanup 2021-08-13 14:09:19 -07:00
datagram.c udp: fix skb_copy_and_csum_datagram with odd segment sizes 2021-02-04 18:56:56 -08:00
datagram.h
dev_addr_lists.c net: dev_addr_list: handle first address in __hw_addr_add_ex 2021-09-30 13:29:09 +01:00
dev_ioctl.c net: core: don't call SIOCBRADD/DELIF for non-bridge devices 2021-08-05 11:36:59 +01:00
dev.c napi: fix race inside napi_enable 2021-09-20 09:41:29 +01:00
devlink.c devlink: Clear whole devlink_flash_notify struct 2021-08-14 13:59:10 +01:00
drop_monitor.c net: Remove redundant if statements 2021-08-05 13:27:50 +01:00
dst_cache.c
dst.c net: Remove redundant if statements 2021-08-05 13:27:50 +01:00
failover.c
fib_notifier.c
fib_rules.c memcg: enable accounting for IP address and routing-related objects 2021-07-20 06:00:38 -07:00
filter.c bpf: tcp: Allow bpf-tcp-cc to call bpf_(get|set)sockopt 2021-08-25 17:40:35 -07:00
flow_dissector.c Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2021-07-31 09:14:46 -07:00
flow_offload.c net: Fix offloading indirect devices dependency on qdisc order creation 2021-08-19 13:19:30 +01:00
gen_estimator.c net_sched: gen_estimator: support large ewma log 2021-01-15 18:11:06 -08:00
gen_stats.c
gro_cells.c gro_cells: reduce number of synchronize_net() calls 2020-11-25 11:28:12 -08:00
hwbm.c
link_watch.c net: linkwatch: fix failure to restore device state across suspend/resume 2021-08-11 14:43:16 -07:00
lwt_bpf.c lwt_bpf: Replace preempt_disable() with migrate_disable() 2020-12-07 11:53:40 -08:00
lwtunnel.c netfilter: add netfilter hooks to SRv6 data plane 2021-08-30 01:51:36 +02:00
Makefile sock_map: Relax config dependency to CONFIG_NET 2021-07-15 18:17:49 -07:00
neighbour.c net: Support filtering interfaces on no master 2021-08-10 16:03:34 -07:00
net_namespace.c net: net_namespace: Optimize the code 2021-08-18 10:34:48 +01:00
net-procfs.c Revert "net: procfs: add seq_puts() statement for dev_mcast" 2021-10-13 17:24:38 -07:00
net-sysfs.c net-sysfs: remove possible sleep from an RCU read-side critical section 2021-03-22 13:28:13 -07:00
net-sysfs.h
net-traces.c tcp: add tracepoint for checksum errors 2021-05-14 15:26:03 -07:00
netclassid_cgroup.c bpf, cgroups: Fix cgroup v2 fallback on v1/v2 mixed mode 2021-09-13 16:35:58 -07:00
netevent.c net: core: Correct function name netevent_unregister_notifier() in the kerneldoc 2021-03-28 17:56:56 -07:00
netpoll.c asm-generic/unaligned: Unify asm/unaligned.h around struct helper 2021-07-02 12:43:40 -07:00
netprio_cgroup.c bpf, cgroups: Fix cgroup v2 fallback on v1/v2 mixed mode 2021-09-13 16:35:58 -07:00
page_pool.c page_pool: use relaxed atomic for release side accounting 2021-08-24 10:46:31 +01:00
pktgen.c pktgen: remove unused variable 2021-09-03 11:48:28 +01:00
ptp_classifier.c bpf: Refactor BPF_PROG_RUN into a function 2021-08-17 00:45:07 +02:00
request_sock.c
rtnetlink.c rtnetlink: fix if_nlmsg_stats_size() under estimation 2021-10-06 15:09:46 +01:00
scm.c memcg: enable accounting for scm_fp_list objects 2021-07-20 06:00:38 -07:00
secure_seq.c crypto: lib/sha1 - remove unnecessary includes of linux/cryptohash.h 2020-05-08 15:32:17 +10:00
selftests.c net: selftests: add MTU test 2021-07-22 00:52:04 -07:00
skbuff.c skbuff: clean up inconsistent indenting 2021-09-03 11:51:26 +01:00
skmsg.c bpf, sockmap: Fix memleak on ingress msg enqueue 2021-07-27 14:55:30 -07:00
sock_diag.c bpf, net: Rework cookie generator as per-cpu one 2020-09-30 11:50:35 -07:00
sock_map.c af_unix: Add unix_stream_proto for sockmap 2021-08-16 18:43:39 -07:00
sock_reuseport.c tcp: Add stats for socket migration. 2021-06-23 12:56:08 -07:00
sock.c af_unix: fix races in sk_peer_pid and sk_peer_cred accesses 2021-09-30 14:18:40 +01:00
stream.c
sysctl_net_core.c net: change netdev_unregister_timeout_secs min value to 1 2021-03-25 17:24:06 -07:00
timestamping.c
tso.c net: tso: add UDP segmentation support 2020-06-18 20:46:23 -07:00
utils.c
xdp.c xdp: Move the rxq_info.mem clearing to unreg_mem_model() 2021-06-28 23:07:59 +02:00