User error, but someone could help them out. Begin forwarded message:
Date: Wed, 16 Dec 2015 15:47:16 +0000 From: "bugzilla-dae...@bugzilla.kernel.org" <bugzilla-dae...@bugzilla.kernel.org> To: "shemmin...@linux-foundation.org" <shemmin...@linux-foundation.org> Subject: [Bug 109471] New: Linux generating invalid Ethernet frames which get dropped (as over-size) by gateway https://bugzilla.kernel.org/show_bug.cgi?id=109471 Bug ID: 109471 Summary: Linux generating invalid Ethernet frames which get dropped (as over-size) by gateway Product: Networking Version: 2.5 Kernel Version: 3.18.11-v7+ #781 SMP PREEMPT armv7l GNU/Linux Hardware: ARM OS: Linux Tree: Mainline Status: NEW Severity: normal Priority: P1 Component: IPV4 Assignee: shemmin...@linux-foundation.org Reporter: linuxb...@gmail.com Regression: No Also described in detail here: http://networkengineering.stackexchange.com/questions/25254/1522-byte-frames-from-access-point-being-dropped-by-gateway I configured the Linux device in question (Raspberry Pi 2b) as a hostap WIFI access point. Wifi clients connect and can sometimes transfer some data but as soon as the packet flow reaches a frame size of 1522 the flow stops - the gateway starts showing a spike in dropped frames (reflected in /sys/class/net/eth0 /statistics/rx_length_errors) as the client retransmits the dropped packets. A closer look shows that the gateway is dropping the packets due to size. The TCP/IP part of the packet is 1500 bytes and I expect framing to add a final 14 or 18 bytes before transmitting it onto the wire. However 22 bytes are being added, and it seems to be too many. I have packet captures available to send via email (I'd like to not attach them for privacy reasons). The following is a sample oversized packet as exported from Wireshark. Note that I tweaked the MAC and IP addresses for privacy. No. Time Source Destination Protocol Length Info 35 21:55:21.644314 192.168.1.149 54.239.25.200 TCP 1522 [TCP Retransmission] 44053→443 [ACK] Seq=350 Ack=155 Win=88832 Len=1460 [ETHERNET FRAME CHECK SEQUENCE INCORRECT] Frame 35: 1522 bytes on wire (12176 bits), 1522 bytes captured (12176 bits) Encapsulation type: Ethernet (1) Arrival Time: Dec 15, 2015 21:55:21.644314000 EST [Time shift for this packet: 0.000000000 seconds] Epoch Time: 1450234521.644314000 seconds [Time delta from previous captured frame: 0.150820000 seconds] [Time delta from previous displayed frame: 3.683211000 seconds] [Time since reference or first frame: 9.568260000 seconds] Frame Number: 35 Frame Length: 1522 bytes (12176 bits) Capture Length: 1522 bytes (12176 bits) [Frame is marked: False] [Frame is ignored: False] [Protocols in frame: eth:ethertype:ip:tcp] [Coloring Rule Name: Bad TCP] [Coloring Rule String: tcp.analysis.flags && !tcp.analysis.window_update] Ethernet II, Src: xx:xx:xx:xx:xx:xx (xx:xx:xx:xx:xx:xx), Dst: Raspberr_xx:xx:xx (xx:xx:xx:xx:xx:xx) Destination: Raspberr_xx:xx:xx (xx:xx:xx:xx:xx:xx) Address: Raspberr_xx:xx:xx (xx:xx:xx:xx:xx:xx) .... ..0. .... .... .... .... = LG bit: Globally unique address (factory default) .... ...0 .... .... .... .... = IG bit: Individual address (unicast) Source: xx:xx:xx:xx:xx:xx (xx:xx:xx:xx:xx:xx) Address: xx:xx:xx:xx:xx:xx (xx:xx:xx:xx:xx:xx) .... ..0. .... .... .... .... = LG bit: Globally unique address (factory default) .... ...0 .... .... .... .... = IG bit: Individual address (unicast) Type: IP (0x0800) Trailer: 2f8e4de5 Frame check sequence: 0x29f37f68 [incorrect, should be 0x3b863a28] [FCS Good: False] [FCS Bad: True] [Expert Info (Error/Checksum): Bad checksum] [Bad checksum] [Severity level: Error] [Group: Checksum] Internet Protocol Version 4, Src: 192.168.1.149 (192.168.1.149), Dst: 54.239.25.200 (54.239.25.200) Version: 4 Header Length: 20 bytes Differentiated Services Field: 0x00 (DSCP 0x00: Default; ECN: 0x00: Not-ECT (Not ECN-Capable Transport)) 0000 00.. = Differentiated Services Codepoint: Default (0x00) .... ..00 = Explicit Congestion Notification: Not-ECT (Not ECN-Capable Transport) (0x00) Total Length: 1500 Identification: 0xaaf3 (43763) Flags: 0x02 (Don't Fragment) 0... .... = Reserved bit: Not set .1.. .... = Don't fragment: Set ..0. .... = More fragments: Not set Fragment offset: 0 Time to live: 64 Protocol: TCP (6) Header checksum: 0x3234 [validation disabled] [Good: False] [Bad: False] Source: 192.168.1.149 (192.168.1.149) Destination: 54.239.25.200 (54.239.25.200) [Source GeoIP: Unknown] [Destination GeoIP: Unknown] Transmission Control Protocol, Src Port: 44053 (44053), Dst Port: 443 (443), Seq: 350, Ack: 155, Len: 1460 Source Port: 44053 (44053) Destination Port: 443 (443) [Stream index: 1] [TCP Segment Len: 1460] Sequence number: 350 (relative sequence number) [Next sequence number: 1810 (relative sequence number)] Acknowledgment number: 155 (relative ack number) Header Length: 20 bytes .... 0000 0001 0000 = Flags: 0x010 (ACK) 000. .... .... = Reserved: Not set ...0 .... .... = Nonce: Not set .... 0... .... = Congestion Window Reduced (CWR): Not set .... .0.. .... = ECN-Echo: Not set .... ..0. .... = Urgent: Not set .... ...1 .... = Acknowledgment: Set .... .... 0... = Push: Not set .... .... .0.. = Reset: Not set .... .... ..0. = Syn: Not set .... .... ...0 = Fin: Not set Window size value: 347 [Calculated window size: 88832] [Window size scaling factor: 256] Checksum: 0x1c58 [validation disabled] [Good Checksum: False] [Bad Checksum: False] Urgent pointer: 0 [SEQ/ACK analysis] [iRTT: 0.028704000 seconds] [Bytes in flight: 2077] [TCP Analysis Flags] [Expert Info (Note/Sequence): This frame is a (suspected) retransmission] [This frame is a (suspected) retransmission] [Severity level: Note] [Group: Sequence] [The RTO for this segment was: 7.247571000 seconds] [RTO based on delta from frame: 12] Retransmitted TCP segment data (1460 bytes) -- You are receiving this mail because: You are the assignee for the bug. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
