I am trying to use this tutorial to connect to the internet from the BeagleBone Black: https://elementztechblog.wordpress.com/2014/12/22/sharing-internet-using-network-over-usb-in-beaglebone-black/
The IpTables steps do not seem to yield the correct configuration. For example:
iptables --table nat -A POSTROUTING -o wlp2s0 -j MASQUERADE
creates the following configuration:
Chain POSTROUTING (policy ACCEPT)
target prot opt source destination
MASQUERADE all -- localhost/16 anywhere
MASQUERADE all -- anywhere anywhere
Why do I have anywhere as destination when I clearly specify wlp2s0 ? Can anyone please help ?
iptables -t nat -L doesn't seem to show additional information like interfaces.
While it's meant to be for save/restore and machine-readable, I much prefer the output of iptables-save due to its completeness.
In your case this should show you the complete configuration for the "nat" table:
iptables-save -t nat
Related
I have a VM in VirtualBox with Debian 10 and I'm trying to NAT masquerade it's output interface (enp0s8) so that it's clients (VMs connected to it) can access the Internet.
All interfaces in the system have an IP. I've already enabled forwarding with:
echo 1 > /proc/sys/net/ipv4/ip_forward
sysctl -w net.ipv4.ip_forward=1
And then I executed:
iptables -t nat -A POSTROUTING -o enp0s8 -j MASQUERADE
However, whenever I execute the above, the following happens:
And no matter how many times I iptables --flush -t nat and repeat the process, the result is always the same. The rule I want to apply is never saved properly and the client's IPs are never masked.
What is the issue here? Almost all tutorials say this is the correct way for masquerading.
I've also tried using nftables, without success.
It is already showing the right output. To show the rules with the interface details, you need to use,
iptables -t nat -L -n -v
And btw, if you have setup NAT networking, it is already taken care to connect outside.
And have you set the default gateway of your clients to this box?
I am unable to use the same target under iptables. can someone help please?
iptables v1.4.21
Kernel: 3.16.7
iptables -t nat -A POSTROUTING -o eth0 -j SAME --to 1.2.3.4-1.2.3.7
iptables: No chain/target/match by that name.
According to iptables-extensions's man page, the SAME target was superseded by the --persistent flag of the DNAT target:
--persistent
Gives a client the same source-/destination-address for each connection. This supersedes the SAME target. Support for persistent mappings is available from 2.6.29-rc2.
I am currently trying to secure a little my server before its release to the world. For now, there is just a Discourse instance running, that uses Mandrill as email smtp server.
There is an nginx server in front of that Discourse.
With no iptables rules, everything works fine. When I apply my rules, it brokes. I am still able to reach the Discourse and even send posts and everything, expect sending email.
With ./launcher mailtest app, it works. The Discourse error, however, is the following : ERREUR - getaddrinfo: Name or service not known.
I really try to find out myself what I should use. But I couldn't.
First, I was thinking a simple iptables -A OUTPUT -p tcp --dport 587 -j ACCEPT was enough, but I was proved the contrary.
Some other inputs :
iptables -F
iptables -P INPUT DROP
iptables -P OUTPUT DROP
iptables -P FORWARD DROP
I set Discourse to use port 587 of Mandrill.
Okay, so I just released... This is not the right SE forum for that question. I'm sorry for that.
However, since I finally found a solution (it's always when you post your question that the question hits you in the face), let me share it.
I was missing a FORWARD rule between docker0 and eth0.
iptables -A FORWARD -i docker0 -o eth0 -j ACCEPT
iptables -A FORWARD -i eth0 -o docker0 -j ACCEPT
Sorry for the inconvenient.
I have 2 kinds of proxies in my local machine : stunnel and TOR-VPN.
stunnel is listening on port 6666
TOR-VPN is listening on port 9040
I want to get web traffic to go to stunnel first and the output traffic of stunnel go to tor-vpn. This needs double redirecting. is it possible to do it with iptables? I mean by using "table nat chain OUTPUT".
Because as far as I know "table nat chain OUTPUT" cant be called twice.
web traffic = browser listening on 127.0.0.1:6666
these are my rules:
iptables -t nat -A OUTPUT -p tcp -j REDIRECT --to-ports 6666
iptables -t nat -A OUTPUT -p tcp -m owner --uid-owner bob -m tcp -j
REDIRECT --to-ports 9040
iptables -t nat -A OUTPUT -p udp -m owner --uid-owner bob -m udp
--dport 53 -j REDIRECT --to-ports 53
iptables -t filter -A OUTPUT -p tcp --dport 6666 -j ACCEPT
iptables -t filter -A OUTPUT -p tcp -m owner --uid-owner bob -m tcp
--dport 9040 -j ACCEPT
iptables -t filter -A OUTPUT -p udp -m owner --uid-owner bob -m udp
--dport 53 -j ACCEPT
iptables -t filter -A OUTPUT -m owner --uid-owner bob -j DROP
the above rules make stunnel work independently from TOR/VPN.
i mean when browser is set with proxy, no traffic will go through TOR/VPN but if i turn off the proxy in browser, all traffic will go through TOR/VPN.
now i want to let browser have the proxy on and all web traffic go to stunnel first, but outgoing stunnel traffic(outgoing loopback traffic) redirects to TOR/VPN(127.0.0.1:9040)
is it possible ? how can i do that? somehow i mean double redirecting inside system.
Policy of all tables is ACCEPT
Checking that this is what you mean :
You have stunnel bound to port 6666 (localhost:6666) and you have tor bound to 9040 (localhost:9040). You want it so your web traffic will go THROUGH stunnel (so destination is localhost:6666) but the OUTBOUND traffic FROM stunnel (with inbound traffic originally from your client redirected to stunnel) should be DESTINED to tor (localhost:9040) ? Is this correct ?
If so, and I am thinking clearly enough (it is just 7:00 and I've been awake far too many hours for a difficult night), this is indeed possible (the reverse is, too). You need to masquerade the destination address (and indeed port) based on the source (address and port (you don't have to specify both, I might add)). Something like this:
iptables -t nat -I PREROUTING -p tcp --sport 6666 -j DNAT --to-destination 9040
If this is not what you mean (or alternatively I made a typo, am not clear headed or being an idiot in some way (in all cases showing myself to be a user as everyone is!), if any it is probably the latter) then please respond. I'll see about enabling email notification so that I see the response. If I don't, however, I apologise in advance.
As an aside: unless you have a final rule in each CHAIN (not table, just as an fyi: a table is filter, nat (which I specify in the above and indeed it is necessary), etc. and CHAIN is INPUT, OUTPUT, FORWARD and others created by the option -N) you shouldn't have -P ACCEPT ('that which is not explicitly permitted is forbidden' and similar wording - i.e. have DROP). The exception is perhaps OUTPUT (but depends on what you need, in the end). However, when dealing with interface 'lo' you'll want to ACCEPT all traffic always, in any case (i.e. specify -i lo and -o lo, depending on chain, and jump to ACCEPT). Of course, maybe you're behind another device but still best practise to not accept anything and everything! (I should also state that you have different chains per table so yes you can specify different tables but the policy is for the chain IN that table)
Edit: something else: no, you don't have to deal with SNAT when you want DNAT and the reverse is true. Anything to the contrary is a misunderstanding. The reason is you're masquerading the CONNECTION. As the man page shows:
It specifies that the destination address of the
packet should be modified (and all future packets in this connection will also be mangled), and rules should cease being examined.
Edit:
If I understand you (now) you actually have two interfaces involved. Or more specifically you need the following:
You have a service you want encrypted. This is tor. Now, you're using stunnel to do this. To this end you want stunnel to forward traffic to tor. Is this right? If yes, then know that stunnel has the following directives (I actually use similar for something else). Here's a mock setup of a service.
[tor]
accept = 6666
connect = 9040
In addition, just as a note: connect can also be a remote address (remote address implies an external address (with port) or even a certain interface (by IP and also with port) on the system (I use external in the sense of you specify ip and port rather than just a port). Furthermore, accept can specify address (with same rules: ip before the port (except that it is obviously on the local machine so no external IP)). You could explain it, perhaps, as stunnel is where the service would bind to except that the service is stunnel and the service it is encrypting is elsewhere (shortly: the bind(2) call allows specific IP or all IPs on the system, and you're basically configuring stunnel to do this).
(And yes, you're right: the sport should have been dport.)
IF this is not what you need then I do not understand all variables. In that case, if you can elaborate on which interfaces (this includes ports and which service per interface) are involved as well as clients involved (and where they send). Because it is a lot more helpful if others know EXACTLY what you need than infer certain parts. Makes it much easier to solve a problem if you know what the problem is entirely. Maybe I've been dense and I should put together it all (and I admit sleep problems - which I have for a long, long time - does not help that, but...) I haven't, I think.
I found the answer by myself. in my first post, i said something that was completely wrong and because of that, i could not do double redirecting.
i said:
Because as far as I know "table nat chain OUTPUT" cant be called twice
it is wrong and "table nat chain OUTPUT" can be called twice. i dont know what exactly i did 2 months ago that thought "table nat chain OUTPUT" cant be called twice.
this is the tables and chains order when using some services on loopback interface or not:
Without having any services on loopback:
Generated packets on local machine -> nat(OUTPUT) -> filter(OUTPUT) -> wlan(ethernet) interface
With having some services on loopback:
Generated packets on local machine -> nat(OUTPUT) -> filter(OUTPUT) -> loopback interface -> nat(OUTPUT) -> filter(OUTPUT) -> wlan(ethernet) interface
these are my rules to solve the problem:
iptables -t nat -A OUTPUT -p tcp -m tcp --dport 6666 -j REDIRECT --to-ports 6666
iptables -t nat -A OUTPUT -p tcp -m owner --uid-owner bob -m tcp -j REDIRECT --to-ports 9040
iptables -t nat -A OUTPUT -p udp -m owner --uid-owner bob -m udp --dport 53 -j REDIRECT --to-ports 53
iptables -t nat -A OUTPUT -d "StunnelServerIp" -o wlan0 -p tcp -j REDIRECT --to-ports 9040
iptables -t filter -A OUTPUT -p tcp -m owner --uid-owner bob -m tcp --dport 9040 -j ACCEPT
iptables -t filter -A OUTPUT -p udp -m owner --uid-owner bob -m udp --dport 53 -j ACCEPT
iptables -t filter -A OUTPUT -p tcp -m tcp --dport 6666 -j ACCEPT
iptables -t filter -A OUTPUT -m owner --uid-owner bob -j DROP
I am facing some problems with tcpreplay. I am running L-7 filter userspace version on ATCA- PP81 blade, and I have this following iptable rules :
iptables -A FORWARD -j NFQUEUE --queue-num 0
iptables -t mangle -A PREROUTING -p udp -i eth0 -j NFQUEUE --queue-num 0
iptables -t mangle -A PREROUTING -p tcp -i eth0 -j NFQUEUE --queue-num 0
I am sending pcap files from a computer using tcpreplay, but all the replayed pcap files except those which have broadcast address were not detected by the iptables. I checked it with:
iptables -t mangle -L -v
I tried many ways, including using a cache file as discussed in some of the forums, and everything is in vain. Now I am totally helpless. I would appreciate it if you could reply my question.
Thanking you in anticipation
regards,
Amlas
It is not possible. This is a tcpreplay limitation.
http://tcpreplay.synfin.net/wiki/FAQ
Can I use IPTables/Traffic Control with tcpreplay?
You can not use iptables/tc on the same box as you run tcpreplay. The only way to use IPTables or Traffic Control (tc) with tcpreplay is to run tcpreplay on a different box and send the traffic through the system running iptables/tc. This limitation is due to how the Linux kernel injects frames vs. reading frames for iptables/tc which makes traffic sent via tcpreplay to be invisible to iptables/tc.