noping crash when traffic to target ip rejected on firewall OUTPUT chain

[zdenek-crha]

Description

Noping crashes (1.9.0) or floods terminal with errors (1.10.0) when trying to send traffic to target host that gets dropped by firewall OUTPUT chain.

$ iptables -A OUTPUT -i  eth0 -d 172.16.0.0/12 -j DROP
$ noping 172.16.0.1
ping_send failed: Operation not permitted
CRASH or screen flooded

Setup explanation

I realize this scenario is not an usual use case. In this section I'll try to add some context on why I'm doing it and what behaviour I would expect.

I use noping for investigating automated test setup when testing network equipment. To ensure our test traffic does not go to incorrect places I configure test machine interfaces like this:

• mgmt interface with FW rule to drop traffic to
• test interface without FW

During the test I configure private network on test interface and send traffic throught it. The FW rule on mgmt interface ensures that I don't get ping responses from outside of test network (due to misconfigured firewalls, routers, ...).

During development I often run noping before test starts, trying to ping hosts that are unreachable. As test runs, I can monitor when test network config was added, when routes have been configured on test devices....

This use is bit troublesome when noping crashes before test network is available (it tries to send traffic through default gw on mgmt interface and then again when network is removed by test.

Proposal

Would it be possible to display red E character and log ping_send failed message in top window. The same way it is done with host unreachable?

OS and noping version:

• Debian Stretch + noping 1.9.0
• Debian Buster + noping 1.10.0