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sysctl: Enable ping(8) inside rootless Podman containers

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This makes ping(8) work without CAP_NET_ADMIN and CAP_NET_RAW because
those aren't effective inside rootless Podman containers.

It's quite useful when using OSTree based operating systems like Fedora
Silverblue, where development environments are often set up using
rootless Podman containers with helpers like Toolbox [1]. Not having
a basic network utility like ping(8) work inside the development
environment can be inconvenient.

See:
https://lwn.net/Articles/422330/
http://man7.org/linux/man-pages/man7/icmp.7.html
https://github.com/containers/libpod/issues/1550

The upper limit of the range of group identifiers is set to 2147483647,
which is 2^31-1. Values greater than that get rejected by the kernel
because of this definition in linux/include/net/ping.h:
  #define GID_T_MAX (((gid_t)~0U) >> 1)

That's not so bad because values between 2^31 and 2^32-1 are reserved
on systemd-based systems anyway [2].

[1] https://github.com/debarshiray/toolbox
[2] https://systemd.io/UIDS-GIDS.html#summary
This commit is contained in:
Debarshi Ray 2019-07-22 21:30:25 +02:00 committed by Lennart Poettering
parent 181824e32c
commit 90ce7627df
2 changed files with 14 additions and 0 deletions
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6
NEWS
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@ -2,6 +2,12 @@ systemd System and Service Manager
CHANGES WITH 243 in spe:
* Enable unprivileged programs, neither setuid nor having file
capabilities, to send ICMP Echo requests by turning on the
net.ipv4.ping_group_range parameter of the Linux kernel for all
groups. If this is not desirable, then it can be disabled by setting
the parameter to "1 0".
* Previously, filters defined with SystemCallFilter= would have the
effect that an calling an offending system call would terminate the
calling thread. This behaviour never made much sense, since killing

8
sysctl.d/50-default.conf
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@ -30,6 +30,14 @@ net.ipv4.conf.all.accept_source_route = 0
# Promote secondary addresses when the primary address is removed
net.ipv4.conf.all.promote_secondaries = 1
# ping(8) without CAP_NET_ADMIN and CAP_NET_RAW
# The upper limit is set to 2^31-1. Values greater than that get rejected by
# the kernel because of this definition in linux/include/net/ping.h:
# #define GID_T_MAX (((gid_t)~0U) >> 1)
# That's not so bad because values between 2^31 and 2^32-1 are reserved on
# systemd-based systems anyway: https://systemd.io/UIDS-GIDS.html#summary
net.ipv4.ping_group_range = 0 2147483647
# Fair Queue CoDel packet scheduler to fight bufferbloat
net.core.default_qdisc = fq_codel