Arch somtimes blocks ports above 1024 to the internet

guano___ · 2013-11-09 17:20:12

I have a small arch box that I use as a torrent machine, and I noticed that sometimes it would not download or upload anything for days. I've tried troubleshooting it, but I don't really know where to look.

First I tried to ping google.com, and got no response, I thought this was weird since I ssh into the box from a computer on the same wifi, and I can reach it fine. It can ping other computers in the network fine though.
I could wget google though, so I started messing around with tracepath to see where the hickup was, and noticed that if I tried to reach anything (non-local) on a port above 1024, the signal wouldn't even reach the router, I would just get this:

[this@htpc ~]$ tracepath google.com -p 1234
1: htpc.lan 0.322ms pmtu 1500
1: no reply
2: no reply
....

Which make some kind of sense, since torrent transfers would use higher ports, and that does work for other computers on the same network. I've been trying to search for all kinds of help, but can't find anything related, and I don't really know where to go from here.
I think the problems all started when I moved the box, and plugged in a usb wifi adapter instead of a wired connection. But the weird part of course is that every now and then (I haven't figured out when), it does work.

Is it the adapter? Could it be the router? Can I do anything to figure out what's happening? Any help is appreciated!

Edit: I'm not running any iptables, and I see nothing in dmesg or journalctl when I try to initiate some kind of network connection.

Last edited by guano___ (2013-11-09 17:21:17)

ewaller · 2013-11-09 17:28:54

I think you've two problems. Yes, the router is probably not forwarding things from the public Internet to your Arch box. Unless you specifically configured it to forward those ports, It is a certainty.

As to your inability to ping Google, that is probably an unrelated DNS problem. See if you can ping Arch Linux using the IP 66.211.214.131 rather than using the domain name.

guano___ · 2013-11-09 17:42:25

Hi, and thanks for the quick response!
I haven't configured any port forwarding on the router, but I believe transmission works it out for itself, how could it otherwise work sometimes? And on my other computers, it's working fine as well.

I can't ping that ip address either, I can run 'wget google.com' without problems though, so it shouldn't be a DNS issue.

WonderWoofy · 2013-11-09 17:50:46

Most torrent clients are setup to use UPnp (universal plug-n-play). This works most of the time, but not always. I have it entirely disable from my router, and simply forward a port to my machine (which works always).

ewaller · 2013-11-09 18:02:55

I thought your concern about lack of activity was about upload, but after I reread it, I see you are concerned about both. So, the download part is probably related to what I think are DNS issues. What are the "Other Computers" on your network?

As to the upload, unless the router is configured to forward torrent ports to your machine, then other torrent users will not be able to connect to your machine and you will not be able to contribute back to the torrent community.
Here is a random article selected from a Google search for "bittorrent router configuration" that talks to the issue.

As to the DNS issue, please post your /etc/resolv.conf file and the output of host -v archlinux.org

ewaller · 2013-11-09 18:04:15

guano___ wrote:

I can't ping that ip address either, I can run 'wget google.com' without problems though, so it shouldn't be a DNS issue.

Any chance something is blocking ARP requests? Either your router, or your ISP?

guano___ · 2013-11-09 18:14:55

I'll have to try configure port forwarding directly on the router then if fixing the other part of the problem doesn't help!

The other computers are two ubuntu laptops (over wifi) and a windows 8 machine (wired connection), they can all ping stuff fine, so that shouldn't be blocked by the router or the isp.

The times transmission has been working on the arch box, both download and upload has worked.

[this@htpc ~]$ cat /etc/resolv.conf
# Generated by dhcpcd from wlp0s29f7u5
# /etc/resolv.conf.head can replace this line
domain lan
nameserver 192.168.1.254
# /etc/resolv.conf.tail can replace this line

[this@htpc ~]$ host -v archlinux.org
Trying "archlinux.org"
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 23375
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 0
;; QUESTION SECTION:
;archlinux.org. IN A
;; ANSWER SECTION:
archlinux.org. 86400 IN A 66.211.214.131
Received 47 bytes from 192.168.1.254#53 in 88 ms
Trying "archlinux.org"
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 27787
;; flags: qr rd ra; QUERY: 1, ANSWER: 0, AUTHORITY: 1, ADDITIONAL: 0
;; QUESTION SECTION:
;archlinux.org. IN AAAA
;; AUTHORITY SECTION:
archlinux.org. 3600 IN SOA ns1.first-ns.de. ibiru.archlinux.org. 2013031400 3600 900 1209600 3600
Received 88 bytes from 192.168.1.254#53 in 61 ms
Trying "archlinux.org"
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 25861
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 0
;; QUESTION SECTION:
;archlinux.org. IN MX
;; ANSWER SECTION:
archlinux.org. 3600 IN MX 10 mail.archlinux.org.
Received 52 bytes from 192.168.1.254#53 in 59 ms

ewaller · 2013-11-09 18:18:38

Okay, that all looks okay to me. I missed that you cannot ping google, but that you can wget it. DNS is probably okay.

Arch Linux

#1 2013-11-09 17:20:12

Arch somtimes blocks ports above 1024 to the internet

#2 2013-11-09 17:28:54

Re: Arch somtimes blocks ports above 1024 to the internet

#3 2013-11-09 17:42:25

Re: Arch somtimes blocks ports above 1024 to the internet

#4 2013-11-09 17:50:46

Re: Arch somtimes blocks ports above 1024 to the internet

#5 2013-11-09 18:02:55

Re: Arch somtimes blocks ports above 1024 to the internet

#6 2013-11-09 18:04:15

Re: Arch somtimes blocks ports above 1024 to the internet

#7 2013-11-09 18:14:55

Re: Arch somtimes blocks ports above 1024 to the internet

#8 2013-11-09 18:18:38

Re: Arch somtimes blocks ports above 1024 to the internet

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