Analysis of packet transmission in a vro Network (1)

This article introduces a basic knowledge about how data packets are transmitted and exchanged in Routers. If you understand this, it will be of great help for you to configure a good network environment.

I. Input Problems

1. The original interface can receive any TCP or UDP packets.

2. To receive the original set of interfaces, the first packet to be received must have a complete and correct IP Address Header. Otherwise, the packet header in ip_rcv () cannot be checked and verified.

3. During the packet received by the original interface, the kernel verifies and verifies the received IP packet, but does not detect or verify any fields in the IP packet. For example, when we create the original set of interfaces, the specified protocol parameter is IPPROTO_TCP, and the kernel does not perform TCP checksum verification, instead, copy all the packets whose protocol field is TCP in the IP header and submit them to the original interface.

4. TCP packets received by the original interface are all packets sorted by TCP after IP address reorganization.

5. If the specified protocol parameter is not zero when the original interface is created (the third parameter of socket), the protocol field of the received datagram should match. Otherwise, the datagram is not transmitted to this interface.

6. If a local IP address is bound to the original interface, the destination IP address of the received datagram should match the bound IP address, otherwise, the packet is not transmitted to this interface.

7. If the original set of interfaces specifies an IP address of the other Party through connect, the source IP address of the received data packet should match the connection address, otherwise, the packet is not transmitted to this interface.

8. If an original set of interfaces is created in the form of protocol parameter 0 and connect or bind is not called, then for each original datagram transmitted by the kernel to the original set of interfaces, this interface will receive a copy.

9. The original set of interfaces cannot receive any ARP or RARP interface, because net_rx_action () will pass ARP or RARP packets to the ARP receiving function class for processing, the receiving function ip_rcv () is not passed to the IP layer ().

10. The original interface does not receive any ICMP data packets, because some ICMP data packets have been responded by the system before they are passed to the original interface, it is not passed to the upper layer.

11. If the packets of the other party are sliced, the original IP packet will be received after the reorganization because the original interface is received at the IP layer.