Bug 211175
| Summary: | gretap does not fragment packets regardless of the DF flag | ||
|---|---|---|---|
| Product: | Networking | Reporter: | Marco Berizzi (pupilla) |
| Component: | IPV4 | Assignee: | Stephen Hemminger (stephen) |
| Status: | RESOLVED DOCUMENTED | ||
| Severity: | normal | CC: | fw |
| Priority: | P1 | ||
| Hardware: | x86-64 | ||
| OS: | Linux | ||
| Kernel Version: | 5.10.4 | Subsystem: | |
| Regression: | No | Bisected commit-id: | |
(In reply to Marco Berizzi from comment #0) > Hello everyone, > > I'm running linux 5.10.4 with iproute-5.10 on Slackware (64bit). > > When I try to configure a gretap device with the "ignore-df" I getting this > error: > > ip link add testgre type gretap remote 10.42.44.6 local 10.86.44.6 ignore-df > RTNETLINK answers: Invalid argument iproute passes 'pmtudisc' by default and ignore-df & pmtudisc are mutually exclusive. try 'ignore-df nopmtudisc'. > Also I have noticed that the icmp datagrams with the DF=none are not > fragmented anyway. > For example this is a tcpdump capture showing a 1459 bytes lenght icmp > packet that is not going to be fragmented and delivered to the other remote > gretap linux box (running the same kernel version). > > ethertype 802.1Q (0x8100), length 1477: vlan 802, p 0, ethertype IPv4, > (flags [none], proto ICMP (1), length 1459) > 192.168.1.247 > 192.168.1.1: ICMP echo request, id 10287, seq 0, length > 1439 Its not clear where this tcpdump was done. Remote? Local? On which interface? Why should this packet be fragmented? Thanks a lot Florian for the hint: indeed the correct parameters are 'ignore-df nopmtudisc'. I think you can safely close this bug report. Thanks again. |
Hello everyone, I'm running linux 5.10.4 with iproute-5.10 on Slackware (64bit). When I try to configure a gretap device with the "ignore-df" I getting this error: ip link add testgre type gretap remote 10.42.44.6 local 10.86.44.6 ignore-df RTNETLINK answers: Invalid argument Instead, if I try to run the following command it is going to be executed: ip link add testgre type gretap remote 10.42.44.6 local 10.86.44.6 noignore-df Also I have noticed that the icmp datagrams with the DF=none are not fragmented anyway. For example this is a tcpdump capture showing a 1459 bytes lenght icmp packet that is not going to be fragmented and delivered to the other remote gretap linux box (running the same kernel version). ethertype 802.1Q (0x8100), length 1477: vlan 802, p 0, ethertype IPv4, (flags [none], proto ICMP (1), length 1459) 192.168.1.247 > 192.168.1.1: ICMP echo request, id 10287, seq 0, length 1439 Is this expected? This is my full gretap setup: eth0 mtu is 1500 bytes. ip link add testgre type gretap remote 10.42.44.6 local 10.86.44.6 ip link set testgre up ip link set eth0 up ip link add name br0 type bridge ip link set br0 up ip link set testgre master br0 ip link set eth0 master br0 and this my 'ip a s' output: 13: testgre@NONE: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1462 qdisc pfifo_fast master br0 state UNKNOWN group default qlen 1000 link/ether 5e:56:0a:0c:12:f0 brd ff:ff:ff:ff:ff:ff 14: br0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1462 qdisc noqueue state UP group default qlen 1000 link/ether 5e:56:0a:0c:12:f0 brd ff:ff:ff:ff:ff:ff