The recently added VRF support in Linux leverages the bind-to-device
API for programs to specify an L3 domain for a socket. While
SO_BINDTODEVICE has been around for ages, not every ipv4/ipv6 capable
program has support for it. Even for those programs that do support it,
the API requires processes to be started as root (CAP_NET_RAW) which
is not desirable from a general security perspective.
This patch set leverages Daniel Mack's work to attach bpf programs to
a cgroup to provide a capability to set sk_bound_dev_if for all
AF_INET{6} sockets opened by a process in a cgroup when the sockets
are allocated.
For example:
1. configure vrf (e.g., using ifupdown2)
auto eth0
iface eth0 inet dhcp
vrf mgmt
auto mgmt
iface mgmt
vrf-table auto
2. configure cgroup
mount -t cgroup2 none /tmp/cgroupv2
mkdir /tmp/cgroupv2/mgmt
test_cgrp2_sock /tmp/cgroupv2/mgmt 15
3. set shell into cgroup (e.g., can be done at login using pam)
echo $$ >> /tmp/cgroupv2/mgmt/cgroup.procs
At this point all commands run in the shell (e.g, apt) have sockets
automatically bound to the VRF (see output of ss -ap 'dev == <vrf>'),
including processes not running as root.
This capability enables running any program in a VRF context and is key
to deploying Management VRF, a fundamental configuration for networking
gear, with any Linux OS installation.
David Ahern (3):
bpf: Refactor cgroups code in prep for new type
bpf: Add new cgroup attach type to enable sock modifications
samples: bpf: add userspace example for modifying sk_bound_dev_if
include/linux/bpf-cgroup.h | 60 ++++++++++++++++++------------
include/uapi/linux/bpf.h | 6 +++
kernel/bpf/cgroup.c | 43 +++++++++++++++++++---
kernel/bpf/syscall.c | 33 ++++++++++-------
net/core/filter.c | 59 ++++++++++++++++++++++++++++++
net/ipv4/af_inet.c | 12 +++++-
net/ipv6/af_inet6.c | 8 ++++
samples/bpf/Makefile | 2 +
samples/bpf/test_cgrp2_sock.c | 83 ++++++++++++++++++++++++++++++++++++++++++
samples/bpf/test_cgrp2_sock.sh | 48 ++++++++++++++++++++++++
10 files changed, 311 insertions(+), 43 deletions(-)
create mode 100644 samples/bpf/test_cgrp2_sock.c
create mode 100755 samples/bpf/test_cgrp2_sock.sh
--
2.1.4
