Linux Network route

First, the basic knowledge of the network:

IP routing table acquired on the device side

[[email protected]/] # Route–n

Kernel IP Routing Table

Destination Gateway genmask Flags Metric Ref use Iface

Default 192.168.1.1 0.0.0.0 UG 0 0 0 apcli0

Default 192.168.2.254 0.0.0.0 UG 0 0 0 ra0

10.8.164.0 0.0.0.0 255.255.255.0 U 0 0 0 eth0

192.168.1.0 0.0.0.0 255.255.255.0 U 0 0 0 apcli0

192.168.2.0 0.0.0.0 255.255.255.0 U 0 0 0 ra0

1 route Command parameters

[Email protected] ~]# route [-nee]
[[email protected] ~]# route add [-net|-host] [domain or host] netmask [mask] [Gw|dev]
[[email protected] ~]# route del [-net|-host] [domain or host] netmask [mask] [Gw|dev]
Parameters of the observation:
-N: Do not use the communication protocol or host name to directly use IP or port number;
-ee: Use more detailed information to display
Add (add) and delete (del) route related parameters:
-net: Indicates that the following route is a domain;
-host: Represents a route that is followed by a connection to a single host;
Netmask: Related to the domain, you can set the netmask to determine the size of the domain;
Gw:gateway, followed by the IP value oh, unlike Dev;
Dev: If you only want to specify that a network card is connected, use this setting, followed by eth0, etc.

Format: route-n
Format:/sbin/route-n
Used to print the routing table, plus the-n parameter is to print the IP address without printing the host name in the output information.

2 Example

Example 1: Displaying the current route

Command:

Route

Route-n

Example 2: Add a gateway/set up a gateway

Command: Route add-net 224.0.0.0 netmask 240.0.0.0 Dev eth0

Example 3: Masking a route

Command: Route add-net 224.0.0.0 netmask 240.0.0.0 Reject

Example 4: Delete a route record

Command:

Route del-net 224.0.0.0 netmask 240.0.0.0

Route del-net 224.0.0.0 netmask 240.0.0.0 Reject

Example 5: Delete and add set default gateway

Command:

Route del default GW 192.168.120.240

Route add default GW 192.168.120.240

3 Related structures and definitions

struct Rtentry

{

unsigned long rt_pad1;

struct SOCKADDR rt_dst;

struct SOCKADDR rt_gateway;

struct SOCKADDR rt_genmask;

unsigned short rt_flags;

Short rt_pad2;

unsigned long rt_pad3;

void *rt_pad4;

Short rt_metric;

Char *rt_dev;

unsigned long rt_mtu;

#ifndef __kernel__

#define RT_MSS RT_MTU

#endif

unsigned long Rt_window;

unsigned short Rt_irtt;

};

#define RTF_UP 0x0001

#define Rtf_gateway 0x0002

#define Rtf_host 0x0004

#define Rtf_reinstate 0x0008

#define RTF_DYNAMIC 0x0010

#define Rtf_modified 0x0020

#define RTF_MTU 0x0040

#define RTF_MSS RTF_MTU

#define Rtf_window 0x0080

#define RTF_IRTT 0x0100

#define Rtf_reject 0x0200

4 control of the underlying kernel

int ioctl (int fd, int request, .../* void *arg */) detailed

The third argument is always a pointer, but the type of the pointer depends on the request parameter. We can divide network-related requests into 6 categories:

Socket interface Operation

File operations

Interface operation

ARP Cache operation

Routing table Operations

Flow System

The following table lists the request parameters for the network-related IOCTL request and the data type that the ARG address must point to:

request                     set     connect     Port         siocatmark     siocspgrp     siocgpgrp             Gets the process ID or process group ID of the socket interface         int     int     int     Text Thing Fionbio Fioasync Fionread Fiosetown Fiogetown Set/clear non-blocking I/O flag Set/clear signal-driven asynchronous I/O flag Gets the number of bytes in the receive buffer Set the process ID or process group ID of the file Gets the process ID or process group ID of the file Int Int Int Int Int Pick up Mouth     siocgifconf     siocsifaddr     siocgifaddr     siocsifflags     siocgifflags     siocsifdstaddr     siocgifdstaddr     siocgifbrdaddr     siocsifbrdaddr     siocgifnetmask     siocsifnetmask     siocgifmetric     siocsifmetric     siocgifmtu     siocxxx     get a list of all interfaces     Set interface address     Get interface address     set interface flag      Get interface flag     set point to address         Get broadcast address     Set broadcast address     get subnet mask     set subnet mask      Gets the measure of the interface         Gets the interface MTU             struct ifconf     struct ifreq     struct ifreq     struct ifreq     struct ifreq     struct ifreq     struct ifreq     struct ifreq     struct ifreq     struct ifreq     struct ifreq     struct ifreq     struct ifreq     struct ifreq     ARP         siocsarp     siocgarp     siocdarp     Create/modify ARP table entry     get ARP table entry     delete arp table entry          struct arpreq     struct arpreq     struct arpreq     Lu By Siocaddrt Siocdelrt Add path Delete Path struct Rtentry struct Rtentry Flow I_xxx

For routing operations, the function that completes the IOCTL is

int ip_rt_ioctl (unsigned int cmd, void *arg), this function determines whether to create a route table entry or delete a route table entry, depending on whether the incoming CMD is SIOCADDRT or SIOCDELRT.

Linux Network route