AF_PACKET capture method is supporting a IPS/Tap mode. In this mode, you justneed the interfaces to be up. Suricata will take care of copying the packetsfrom one interface to the other. No iptables or nftables configuration isnecessary.
VM1 and 2 are on same subnet. Bridge has 2 interfaces added to brctl bridge.When I block VM2 ip using uptables -A FORWARD -s (VM1 ip) -j DENYit doesn't work.I understand the packet never goes to network layer but this says "all iptables chains will be traversed while the IP packet is in the bridge code". Even MAC filtering doesn't work on iptables. ebtables work fine. What is wrong?
iptables.sh Bridge mode
Download File: https://trenalocra.blogspot.com/?vk=2vCTXU
Linux' bridge filter framework has available mechanisms where the layer 2 bridge code can do an upcall to iptables (as well as arptables or ip6tables) and have filtering travel from layer 2 (bridged frames) through layer 3 (iptables with packets) and then back to layer 2. This is much beyond the use the BROUTING chain which only gives the logical choice of staying at layer 2 or continuing at layer 3 (by doing a frame dnat/broute to local).
It also caused troubles when people didn't expect this to happen and got issues hard to debug, or hindered performances when it was (most of the time) not needed. So starting with kernel 3.18, the br_netfilter code was split from the bridge code and modularized and is not automatically loaded anymore.
To use this feature now with iptables, one has to modprobe br_netfilter and keep the sysconf parameter net.bridge.bridge-nf-call-iptables set to 1 (equivalent to echo 1 > /proc/sys/net/bridge/bridge-nf-call-iptables). This will now allow all the wonderful complexity of OP's link: ebtables/iptables interaction on a Linux-based bridge. Note that this module can also be automatically loaded when iptables uses the physdev) match and this can subtly alter the whole firewall behaviour if not careful when using both ebtables and iptables.
Note: nftables (as well as iptables-nft) is also affected. The current status is considered a bit messy (because of layering violations' additional complexity) and some reorganization was done to have direct conntrack support in the bridge path without using br_netfilter anymore: since kernel 5.3 Linux provides the kernel module nf_conntrack_bridge allowing nftables to handle connection tracking directly in the bridge layer without reaching the ip (nor ip6 and inet) families: connection tracking support for bridge.
The explanation is that the bridge netfilter code is enabled by Docker for internal container isolation: intended among other usages for stateful bridge firewalling or for leveraging iptables' matches and targets from bridge path without having to (or being able to) duplicate them all in ebtables. Quite disregarding network layering, the ethernet bridge code, at network layer 2, now makes upcalls to iptables working at IP level, ie network layer 3. It can be enabled only globally before kernel 5.3 (but Docker doesn't handle the new kernel 5.3 features): either for host and every containers, or for none. Once understood what's going and knowing what to look for, adapted choices can be made.
The netfilter project describes the various ebtables/iptables interactions when br_netfilter is enabled. Especially of interest is the section 7 explaining why some rules without apparent effect are sometimes needed to avoid unintended effects from the bridge path, like using:
Those rules should never match because traffic in the same IP LAN is not routed, except for some rare DNAT setups. But thanks to br_netfilter they do match, because they are first called for switched frames ("upgraded" to IP packets) traversing the bridge. Then they are called again for routed packets traversing the router to an unrelated interface (but won't match then).
Don't put an IP on the bridge: put that IP on one end of a veth interface with its other end on the bridge: this should ensure that the bridge won't interact with routing, but that's not what are doing most container/VM common products.
Switch everything to nftables which among stated goals will avoid these bridge interaction issues. For now the bridge firewalling has no stateful support available, it's still WIP but is promised to be cleaner when available, because there won't be any "upcall".
Let's reproduce a simple case similar with many container usages: a router 192.168.0.1/192.0.2.100 doing NAT with two hosts behind: 192.168.0.101 and 192.168.0.102, linked with a bridge on the router. The two hosts can communicate directly on the same LAN, through the bridge.
... instead of source 192.168.0.101. The MASQUERADE rule was also called from the bridge path. To avoid this either add (as explained in section 7's example) an exception rule before, or state a non-bridge outgoing interface, if possible at all (now it's available you can even use -m physdev if it has to be a bridge...).
netfilter-dev: connection tracking support for bridge: WIP bridge netfilter code to prepare stateful bridge firewalling using nftables, this time more elegantly. I think one of the last steps to get rid of iptables ('s kernel side API). UPDATE: added in kernel 5.3, but as long as there's no complete rework in Docker to use these features, doesn't change anything.
This is a great resource to read about the interaction and this one details the functionality of br-nf code, including how to disable all or some of the functionalities (i.e. not passing bridge traffic to iptables).
19. Now you should finally have a fully operational Raspberry Pi WiFi Bridge, you can ensure this is working by plugging any device into its Ethernet port, the bridge should provide an internet connection to the device you plugged it into.
Modes for the init container can be changed either at upgrade time, or duringinstallation. Once configured, all injected workloads (including the controlplane) will use the same mode in the init container. Both modes will use theiptables utility to configure firewall rules; the main difference between thetwo, is which binary they will call into:
Conceptually, iptables-nft is a bridge between the legacy and the newernftables utilities. Under the hood, it uses a different backend, where rulesadditions and deletions are atomic. The nft version of iptables uses the samepacket matching syntax (xtables) as its legacy counterpart.
The mode for linkerd-init can be overridden through the configuration optionproxyInit.iptablesMode=iptablesnft. The configuration option can be used forboth Helm and CLI installations (or upgrades). For example, the following linewill install Linkerd and set the init container mode to nft:
A bridge is a piece of software used to unite two or more network segments. A bridge behaves like a virtual network switch, working transparently (the other machines do not need to know about its existence). Any real devices (e.g. eth0) and virtual devices (e.g. tap0) can be connected to it.
GNOME's Network settings can create bridges, but currently will not auto-connect to them or slave/attached interfaces. Open Network Settings, add a new interface of type Bridge, add a new bridged connection, and select the MAC address of the device to attach to the bridge.
KDE's plasma-nm can create bridges. In order to view, create and modify bridge interfaces open the Connections window either by right clicking the Networks applet in the system tray and selecting Configure Network Connections... or from System Settings > Connections. Click the Configuration button in the lower left corner of the module and enable "Show virtual connections". A session restart will be necessary to use the enabled functionality.
If NetworkManager's default interface for the device you added to the bridge connects automatically, you may want to disable that by clicking the gear next to it in Network Settings, and unchecking "Connect automatically" under "Identity."
To add a wireless interface to a bridge, you first have to assign the wireless interface to an access point or start an access point with hostapd. Otherwise the wireless interface will not be added to the bridge.
In some situations the bridge not only serves as a bridge box, but also talks to other hosts. Packets that arrive on a bridge port and that are destinated to the bridge box itself will by default enter the iptables INPUT chain with the logical bridge port as input device. These packets will be queued twice by the network code, the first time they are queued after they are received by the network device. The second time after the bridge code examined the destination MAC address and determined it was a locally destinated packet and therefore decided to pass the frame up to the higher protocol stack.[1]
The way to let locally destinated packets be queued only once is by brouting them in the BROUTING chain of the broute table. Suppose br0 has an IP address and that br0's bridge ports do not have an IP address. Using the following rule should make all locally directed traffic be queued only once:
The replies from the bridge will be sent out through the br0 device (assuming your routing table is correct and sends all traffic through br0), so everything keeps working neatly, without the performance loss caused by the packet being queued twice.
The redirect target is needed because the MAC address of the bridge port is not necessarily equal to the MAC address of the bridge device. The packets destinated to the bridge box will have a destination MAC address equal to that of the bridge br0, so that destination address must be changed to that of the bridge port.
Now IP address and route for the earlier configured bridge must be set. This is usually done by starting a DHCP client for this interface. Otherwise, consult Network configuration for manual configuration.
As the MAC address of the bridge is not necessarily equal to the MAC address of the networking card usually used by the server, the server provider might drop traffic coming out from the bridge, resulting in a loss of connectivity when bridging e.g. the server ethernet interface. Configuring the bridge to clone the mac address of the ethernet interface might therefore be needed for hosted servers. 2ff7e9595c
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