linux下的ifconfig源码有些看不懂，请指教~
最近一直在看linux下的命令源码不是很明白
有经验的能不能指点下
谢谢了~ 代码如下：
/* ifconfig
*
* Similar to the standard Unix ifconfig, but with only the necessary
* parts for AF_INET, and without any printing of if info (for now).
*
* Bjorn Wesen, Axis Communications AB
*
*
* Authors of the original ifconfig was:
* Fred N. van Kempen, <[email protected]>
*
* This program is free software; you can redistribute it
* and/ormodify it underthe terms ofthe GNU General
* PublicLicense aspublishedbytheFreeSoftware
* Foundation;eitherversion 2 of the License, or(at
* your option) any later version.
*
* $Id: ifconfig.c,v 1.14 2001/10/28 05:14:46 andersen Exp $
*
*/
/*
* Heavily modified by Manuel Novoa III Mar 6, 2001
*
* From initial port to busybox, removed most of the redundancy by
* converting to a table-driven approach.Added several (optional)
* args missing from initial port.
*
* Still missing:media, tunnel.
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h> // strcmp and friends
#include <ctype.h> // isdigit and friends
#include <stddef.h> /* offsetof */
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/ioctl.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <net/if.h>
#include <net/if_arp.h>
#include <linux/if_ether.h>
#include "busybox.h"
#ifdef BB_FEATURE_IFCONFIG_SLIP
#include <linux/if_slip.h>
#endif
/* I don't know if this is needed for busybox or not.Anyone? */
#define QUESTIONABLE_ALIAS_CASE
/* Defines for glibc2.0 users. */
#ifndef SIOCSIFTXQLEN
#define SIOCSIFTXQLEN 0x8943
#define SIOCGIFTXQLEN 0x8942
#endif
/* ifr_qlen is ifru_ivalue, but it isn't present in 2.0 kernel headers */
#ifndef ifr_qlen
#define ifr_qlen ifr_ifru.ifru_mtu
#endif
#ifndef IFF_DYNAMIC
#define IFF_DYNAMIC 0x8000/* dialup device with changing addresses */
#endif
/*
* Here are the bit masks for the "flags" member of struct options below.
* N_ signifies no arg prefix; M_ signifies arg prefixed by '-'.
* CLR clears the flag; SET sets the flag; ARG signifies (optional) arg.
*/
#define N_CLR 0x01
#define M_CLR 0x02
#define N_SET 0x04
#define M_SET 0x08
#define N_ARG 0x10
#define M_ARG 0x20
#define M_MASK (M_CLR | M_SET | M_ARG)
#define N_MASK (N_CLR | N_SET | N_ARG)
#define SET_MASK (N_SET | M_SET)
#define CLR_MASK (N_CLR | M_CLR)
#define SET_CLR_MASK (SET_MASK | CLR_MASK)
#define ARG_MASK (M_ARG | N_ARG)
/*
* Here are the bit masks for the "arg_flags" member of struct options below.
*/
/*
* cast type:
* 00 int
* 01 char *
* 02 HOST_COPY in_ether
* 03 HOST_COPY INET_resolve
*/
#define A_CAST_TYPE 0x03
/*
* map type:
* 00 not a map type (mem_start, io_addr, irq)
* 04 memstart (unsigned long)
* 08 io_addr(unsigned short)
* 0C irq (unsigned char)
*/
#define A_MAP_TYPE 0x0C
#define A_ARG_REQ 0x10 /* Set if an arg is required. */
#define A_NETMASK 0x20 /* Set if netmask (check for multiple sets). */
#define A_SET_AFTER 0x40 /* Set a flag at the end. */
#define A_COLON_CHK 0x80 /* Is this needed?See below. */
/*
* These defines are for dealing with the A_CAST_TYPE field.
*/
#define A_CAST_CHAR_PTR0x01
#define A_CAST_RESOLVE 0x01
#define A_CAST_HOST_COPY 0x02
#define A_CAST_HOST_COPY_IN_ETHER A_CAST_HOST_COPY
#define A_CAST_HOST_COPY_RESOLVE (A_CAST_HOST_COPY | A_CAST_RESOLVE)
/*
* These defines are for dealing with the A_MAP_TYPE field.
*/
#define A_MAP_ULONG 0x04 /* memstart */
#define A_MAP_USHORT 0x08 /* io_addr */
#define A_MAP_UCHAR 0x0C /* irq */
/*
* Define the bit masks signifying which operations to perform for each arg.
*/
#define ARG_METRIC (A_ARG_REQ /*| A_CAST_INT*/)
#define ARG_MTU (A_ARG_REQ /*| A_CAST_INT*/)
#define ARG_TXQUEUELEN (A_ARG_REQ /*| A_CAST_INT*/)
#define ARG_MEM_START (A_ARG_REQ | A_MAP_ULONG)
#define ARG_IO_ADDR (A_ARG_REQ | A_MAP_ULONG)
#define ARG_IRQ (A_ARG_REQ | A_MAP_UCHAR)
#define ARG_DSTADDR (A_ARG_REQ | A_CAST_HOST_COPY_RESOLVE)
#define ARG_NETMASK (A_ARG_REQ | A_CAST_HOST_COPY_RESOLVE | A_NETMASK)
#define ARG_BROADCAST (A_ARG_REQ | A_CAST_HOST_COPY_RESOLVE | A_SET_AFTER)
#define ARG_HW (A_ARG_REQ | A_CAST_HOST_COPY_IN_ETHER)
#define ARG_POINTOPOINT(A_CAST_HOST_COPY_RESOLVE | A_SET_AFTER)
#define ARG_KEEPALIVE (A_ARG_REQ | A_CAST_CHAR_PTR)
#define ARG_OUTFILL (A_ARG_REQ | A_CAST_CHAR_PTR)
#define ARG_HOSTNAME (A_CAST_HOST_COPY_RESOLVE | A_SET_AFTER | A_COLON_CHK)
/*
* Set up the tables.Warning!They must have corresponding order!
*/
struct arg1opt {
const char *name;
unsigned short selector;
unsigned short ifr_offset;
};
struct options {
const char *name;
const unsigned char flags;
const unsigned char arg_flags;
const unsigned short selector;
};
#define ifreq_offsetof(x)offsetof(struct ifreq, x)
static const struct arg1opt Arg1Opt[] = {
{"SIOCSIFMETRIC",SIOCSIFMETRIC,ifreq_offsetof(ifr_metric)},
{"SIOCSIFMTU", SIOCSIFMTU, ifreq_offsetof(ifr_mtu)},
{"SIOCSIFTXQLEN",SIOCSIFTXQLEN,ifreq_offsetof(ifr_qlen)},
{"SIOCSIFDSTADDR", SIOCSIFDSTADDR, ifreq_offsetof(ifr_dstaddr)},
{"SIOCSIFNETMASK", SIOCSIFNETMASK, ifreq_offsetof(ifr_netmask)},
{"SIOCSIFBRDADDR", SIOCSIFBRDADDR, ifreq_offsetof(ifr_broadaddr)},
#ifdef BB_FEATURE_IFCONFIG_HW
{"SIOCSIFHWADDR",SIOCSIFHWADDR,ifreq_offsetof(ifr_hwaddr)},
#endif
{"SIOCSIFDSTADDR", SIOCSIFDSTADDR, ifreq_offsetof(ifr_dstaddr)},
#ifdef SIOCSKEEPALIVE
{"SIOCSKEEPALIVE", SIOCSKEEPALIVE, ifreq_offsetof(ifr_data)},
#endif
#ifdef SIOCSOUTFILL
{"SIOCSOUTFILL", SIOCSOUTFILL, ifreq_offsetof(ifr_data)},
#endif
#ifdef BB_FEATURE_IFCONFIG_MEMSTART_IOADDR_IRQ
{"SIOCSIFMAP", SIOCSIFMAP, ifreq_offsetof(ifr_map.mem_start)},
{"SIOCSIFMAP", SIOCSIFMAP, ifreq_offsetof(ifr_map.base_addr)},
{"SIOCSIFMAP", SIOCSIFMAP, ifreq_offsetof(ifr_map.irq)},
#endif
/* Last entry if for unmatched (possibly hostname) arg. */
{"SIOCSIFADDR", SIOCSIFADDR, ifreq_offsetof(ifr_addr)},
};
static const struct options OptArray[] = {
{"metric", N_ARG, ARG_METRIC, 0},
{"mtu", N_ARG, ARG_MTU, 0},
{"txqueuelen", N_ARG, ARG_TXQUEUELEN,0},
{"dstaddr", N_ARG, ARG_DSTADDR, 0},
{"netmask", N_ARG, ARG_NETMASK, 0},
{"broadcast", N_ARG | M_CLR, ARG_BROADCAST, IFF_BROADCAST},
#ifdef BB_FEATURE_IFCONFIG_HW
{"hw", N_ARG, ARG_HW, 0},
#endif
{"pointopoint",N_ARG | M_CLR, ARG_POINTOPOINT, IFF_POINTOPOINT},
#ifdef SIOCSKEEPALIVE
{"keepalive", N_ARG, ARG_KEEPALIVE, 0},
#endif
#ifdef SIOCSOUTFILL
{"outfill", N_ARG, ARG_OUTFILL, 0},
#endif
#ifdef BB_FEATURE_IFCONFIG_MEMSTART_IOADDR_IRQ
{"mem_start", N_ARG, ARG_MEM_START, 0},
{"io_addr", N_ARG, ARG_IO_ADDR, 0},
{"irq", N_ARG, ARG_IRQ, 0},
#endif
{"arp", N_CLR | M_SET, 0, IFF_NOARP},
{"trailers", N_CLR | M_SET, 0, IFF_NOTRAILERS},
{"promisc", N_SET | M_CLR, 0, IFF_PROMISC},
{"multicast", N_SET | M_CLR, 0, IFF_MULTICAST},
{"allmulti", N_SET | M_CLR, 0, IFF_ALLMULTI},
{"dynamic", N_SET | M_CLR, 0, IFF_DYNAMIC},
{"up", N_SET , 0, (IFF_UP | IFF_RUNNING)},
{"down", N_CLR , 0, IFF_UP},
{ NULL, 0, ARG_HOSTNAME, (IFF_UP | IFF_RUNNING)}
};
/*
* A couple of prototypes.
*/
#ifdef BB_FEATURE_IFCONFIG_HW
static int in_ether(char *bufp, struct sockaddr *sap);
#endif
#ifdef BB_FEATURE_IFCONFIG_STATUS
extern int interface_opt_a;
extern int display_interfaces(char *ifname);
#endif
/*
* Our main function.
*/
int ifconfig_main(int argc, char **argv)
{
struct ifreq ifr;
struct sockaddr_in sai;
#ifdef BB_FEATURE_IFCONFIG_HW
struct sockaddr sa;
#endif
const struct arg1opt *a1op;
const struct options *op;
int sockfd;/* socket fd we use to manipulate stuff with */
int goterr;
int selector;
char *p;
char host;
unsigned char mask;
unsigned char did_flags;
goterr = 0;
did_flags = 0;
/* skip argv */
++argv;
--argc;
#ifdef BB_FEATURE_IFCONFIG_STATUS
if ((argc > 0) && (strcmp(*argv,"-a") == 0)) {
interface_opt_a = 1;
--argc;
++argv;
}
#endif
if(argc <= 1) {
#ifdef BB_FEATURE_IFCONFIG_STATUS
return display_interfaces(argc ? *argv : NULL);
#else
error_msg_and_die( "ifconfig was not compiled with interface status display support.");
#endif
}
/* Create a channel to the NET kernel. */
if ((sockfd = socket(AF_INET, SOCK_DGRAM, 0)) < 0) {
perror_msg_and_die("socket");
}
/* get interface name */
safe_strncpy(ifr.ifr_name, *argv, IFNAMSIZ);
/* Process the remaining arguments. */
while (*++argv != (char *) NULL) {
p = *argv;
mask = N_MASK;
if (*p == '-') { /* If the arg starts with '-'... */
++p; /* advance past it and */
mask = M_MASK; /* set the appropriate mask. */
}
for (op = OptArray ; op->name ; op++) { /* Find table entry. */
if (strcmp(p,op->name) == 0) { /* If name matches... */
if ((mask &= op->flags)) { /* set the mask and go. */
goto FOUND_ARG;;
}
/* If we get here, there was a valid arg with an */
/* invalid '-' prefix. */
++goterr;
goto LOOP;
}
}
/* We fell through, so treat as possible hostname. */
a1op = Arg1Opt + (sizeof(Arg1Opt) / sizeof(Arg1Opt)) - 1;
mask = op->arg_flags;
goto HOSTNAME;
FOUND_ARG:
if (mask & ARG_MASK) {
mask = op->arg_flags;
a1op = Arg1Opt + (op - OptArray);
if (mask & A_NETMASK & did_flags) {
show_usage();
}
if (*++argv == NULL) {
if (mask & A_ARG_REQ) {
show_usage();
} else {
--argv;
mask &= A_SET_AFTER; /* just for broadcast */
}
} else { /* got an arg so process it */
HOSTNAME:
did_flags |= (mask & A_NETMASK);
if (mask & A_CAST_HOST_COPY) {
#ifdef BB_FEATURE_IFCONFIG_HW
if (mask & A_CAST_RESOLVE) {
#endif
safe_strncpy(host, *argv, (sizeof host));
sai.sin_family = AF_INET;
sai.sin_port = 0;
if (!strcmp(host, "default")) {
/* Default is special, meaning 0.0.0.0. */
sai.sin_addr.s_addr = INADDR_ANY;
} else if (inet_aton(host, &sai.sin_addr) == 0) {
/* It's not a dotted quad. */
++goterr;
continue;
}
p = (char *) &sai;
#ifdef BB_FEATURE_IFCONFIG_HW
} else { /* A_CAST_HOST_COPY_IN_ETHER */
/* This is the "hw" arg case. */
if (strcmp("ether", *argv) || (*++argv == NULL)) {
show_usage();
}
safe_strncpy(host, *argv, (sizeof host));
if (in_ether(host, &sa)) {
fprintf(stderr, "invalid hw-addr %s\n", host);
++goterr;
continue;
}
p = (char *) &sa;
}
#endif
memcpy((((char *)(&ifr)) + a1op->ifr_offset),
p, sizeof(struct sockaddr));
} else {
unsigned int i = strtoul(*argv,NULL,0);
p = ((char *)(&ifr)) + a1op->ifr_offset;
#ifdef BB_FEATURE_IFCONFIG_MEMSTART_IOADDR_IRQ
if (mask & A_MAP_TYPE) {
if (ioctl(sockfd, SIOCGIFMAP, &ifr) < 0) {
++goterr;
continue;
}
if ((mask & A_MAP_UCHAR) == A_MAP_UCHAR) {
*((unsigned char *) p) = i;
} else if (mask & A_MAP_USHORT) {
*((unsigned short *) p) = i;
} else {
*((unsigned long *) p) = i;
}
} else
#endif
if (mask & A_CAST_CHAR_PTR) {
*((caddr_t *) p) = (caddr_t) i;
} else { /* A_CAST_INT */
*((int *) p) = i;
}
}
if (ioctl(sockfd, a1op->selector, &ifr) < 0) {
perror(a1op->name);
++goterr;
continue;
}
#ifdef QUESTIONABLE_ALIAS_CASE
if (mask & A_COLON_CHK) {
/*
* Don't do the set_flag() if the address is an alias with
* a - at the end, since it's deleted already! - Roman
*
* Should really use regex.h here, not sure though how well
* it'll go with the cross-platform support etc.
*/
char *ptr;
short int found_colon = 0;
for (ptr = ifr.ifr_name; *ptr; ptr++ ) {
if (*ptr == ':') {
found_colon++;
}
}
if (found_colon && *(ptr - 1) == '-') {
continue;
}
}
#endif
}
if (!(mask & A_SET_AFTER)) {
continue;
}
mask = N_SET;
}
if (ioctl(sockfd, SIOCGIFFLAGS, &ifr) < 0) {
perror("SIOCGIFFLAGS");
++goterr;
} else {
selector = op->selector;
if (mask & SET_MASK) {
ifr.ifr_flags |= selector;
} else {
ifr.ifr_flags &= ~selector;
}
if (ioctl(sockfd, SIOCSIFFLAGS, &ifr) < 0) {
perror("SIOCSIFFLAGS");
++goterr;
}
}
LOOP:
} /* end of while-loop */
return goterr;
}
#ifdef BB_FEATURE_IFCONFIG_HW
/* Input an Ethernet address and convert to binary. */
static int
in_ether(char *bufp, struct sockaddr *sap)
{
unsigned char *ptr;
int i, j;
unsigned char val;
unsigned char c;
sap->sa_family = ARPHRD_ETHER;
ptr = sap->sa_data;
for (i = 0 ; i < ETH_ALEN ; i++) {
val = 0;
/* We might get a semicolon here - not required. */
if (i && (*bufp == ':')) {
bufp++;
}
for (j=0 ; j<2 ; j++) {
c = *bufp;
if (c >= '0' && c <= '9') {
c -= '0';
} else if (c >= 'a' && c <= 'f') {
c -= ('a' - 10);
} else if (c >= 'A' && c <= 'F') {
c -= ('A' - 10);
} else if (j && (c == ':' || c == 0)) {
break;
} else {
return -1;
}
++bufp;
val <<= 4;
val += c;
}
*ptr++ = val;
}
return (int) (*bufp); /* Error if we don't end at end of string. */
}
#endif 能给个大概思路吗？ 能给个大概思路吗？
你这个全部的ifconfig源代码吗
你这是全部的ifconfig的源代码吗，我可以给你解答解答：qq:7769512
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