On 12/5/17 3:46 PM, Kevin Cernekee wrote:
> Currently, a nlmon link inside a child namespace can observe systemwide
> netlink activity. Filter the traffic so that in a non-init netns,
> nlmon can only sniff netlink messages from its own netns.
>
> Test case:
>
> vpnns -- bash -c "ip link add nlmon0 type nlmon; \
> ip link set nlmon0 up; \
> tcpdump -i nlmon0 -q -w /tmp/nlmon.pcap -U" &
> sudo ip xfrm state add src 10.1.1.1 dst 10.1.1.2 proto esp \
> spi 0x1 mode transport \
> auth sha1 0x6162633132330000000000000000000000000000 \
> enc aes 0x00000000000000000000000000000000
> grep abc123 /tmp/nlmon.pcap
>
> Signed-off-by: Kevin Cernekee <cerne...@chromium.org>
> ---
> net/netlink/af_netlink.c | 5 +++++
> 1 file changed, 5 insertions(+)
>
> diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
> index b9e0ee4..88381a2 100644
> --- a/net/netlink/af_netlink.c
> +++ b/net/netlink/af_netlink.c
> @@ -253,6 +253,11 @@ static int __netlink_deliver_tap_skb(struct sk_buff *skb,
> struct sock *sk = skb->sk;
> int ret = -ENOMEM;
>
> + if (!net_eq(dev_net(dev), sock_net(sk)) &&
> + !net_eq(dev_net(dev), &init_net)) {
Why is init_net special? Seems like snooping should be limited to the
namespace you are in.
