iptables, bridging and inside-/outside-issue
After reading through the article series by Mick Bauer regarding transparent firewalls I got a bit inspired to try for myself.
I've installed ubuntu onto a machine with 3 network interfaces, and bridged these three interfaces to one common bridge.
I've copied the iptables-script from part V in the series, but re-written it due to the fact that I in my installation will be unable to sort traffic based on ip.
I will not know which addresses will be used on either side of the firewall, so I'll have to sort my traffic on some other variable.
I was thinking that I could sort the traffic based on PHYSIN and PHYSOUT in iptables, but -i and -o does not seem to do that.
As an example I've created the following rule:
iptables -A FORWARD -i eth1 -o eth0 -p tcp --dport 80 -j ACCEPT
But I still get the following in my kernel log:
floyd kernel: [269519.979985] Dropped by default (FORWARD): IN=br0 OUT=br0 PHYSIN=eth1 PHYSOUT=eth0 SRC=10.0.0.113 DST=22.214.171.124 LEN=60 TOS=0x00 PREC=0x00 TTL=64 ID=31771 DF PROTO=TCP SPT=35727 DPT=80 WINDOW=5840 RES=0x00 SYN URGP=0
Which as far as I can figure should be allowed by the rule.
What can I do to sort the traffic based on the physical interface?
Fast/Flexible Linux OS Recovery
On Demand Now
In this live one-hour webinar, learn how to enhance your existing backup strategies for complete disaster recovery preparedness using Storix System Backup Administrator (SBAdmin), a highly flexible full-system recovery solution for UNIX and Linux systems.
Join Linux Journal's Shawn Powers and David Huffman, President/CEO, Storix, Inc.
Free to Linux Journal readers.Register Now!
- Ubuntu Online Summit
- Devuan Beta Release
- The Qt Company's Qt Start-Up
- Download "Linux Management with Red Hat Satellite: Measuring Business Impact and ROI"
- May 2016 Issue of Linux Journal
- The US Government and Open-Source Software
- Open-Source Project Secretly Funded by CIA
- The Death of RoboVM
- New Container Image Standard Promises More Portable Apps
- EnterpriseDB's EDB Postgres Advanced Server and EDB Postgres Enterprise Manager
In modern computer systems, privacy and security are mandatory. However, connections from the outside over public networks automatically imply risks. One easily available solution to avoid eavesdroppers’ attempts is SSH. But, its wide adoption during the past 21 years has made it a target for attackers, so hardening your system properly is a must.
Additionally, in highly regulated markets, you must comply with specific operational requirements, proving that you conform to standards and even that you have included new mandatory authentication methods, such as two-factor authentication. In this ebook, I discuss SSH and how to configure and manage it to guarantee that your network is safe, your data is secure and that you comply with relevant regulations.Get the Guide