I have a weird problem when I try to post contents or upload files by php to my server.
After submitting the form it sleeps for a while then shows a page loading error. I tried different contents and files with different sizes and found that it only can post/upload contents/files with size bellow 530 bytes! (approximately).
I can upload/post to the other sites, so I'm pretty sure the issue is on the server somewhere.
The server is connected to the internet via a PPPoE connection, and I've previously had problems with FTP which I solved by reducing the server's MTU to 1460, however now even changing MTU doesn't help.
When I monitor the network through WireShark the lines below are shown (checksum error and bad tcp)
1170 53.165583000 192.168.1.2 22.214.171.124 TCP 1506 [TCP segment of a reassembled PDU] 1293 57.661244000 192.168.1.2 126.96.36.199 TCP 1506 [TCP Retransmission] 60849 > http [ACK] Seq=1 Ack=1 Win=66792 Len=1452
in the details of lines it says the error occurs on IP packets and mainly because of incorrect checksum (its 0x0000), and suggests that it may be caused by the TCP/IP checksum offload functionality.
Could this be related to my issue? If so, how should I solve it? Should I disable checksums? Change the NIC? Something else?
Update: I disabled the ip checksum in my computer (client) and now I see another message on TCP retransmission which is suspected to be the cause of the problem
[This frame is a (suspected) retrasmission]
[TCP Analysis Flags]
it seems to me a congestion error, but I don't know how to solve it