我从http://ftp.cc.uoc.gr/mirrors/OpenBSD/src/usr.sbin/tcpdump/print-lldp.c获得的以下代码，使用Ubuntu作为我的基本操作系统，将LLDP功能包含在我的项目中。
/* $OpenBSD: print-lldp.c,v 1.6 2009/11/12 00:02:16 deraadt Exp $ */
/*
* Copyright (c) 2006 Reyk Floeter <reyk@openbsd.org>
*
* Permission to use, copy, modify, and distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
#include <sys/param.h>
#include <sys/time.h>
#include <sys/socket.h>
#include <net/if.h>
#include <netinet/in.h>
#include <netinet/in_systm.h>
#include <netinet/if_ether.h>
#include <arpa/inet.h>
#include <ctype.h>
#include <stdio.h>
#include <string.h>
#include "addrtoname.h"
#include "extract.h"
#include "interface.h"
#include "afnum.h"
enum {
LLDP_TLV_END = 0,
LLDP_TLV_CHASSIS_ID = 1,
LLDP_TLV_PORT_ID = 2,
LLDP_TLV_TTL = 3,
LLDP_TLV_PORT_DESCR = 4,
LLDP_TLV_SYSTEM_NAME = 5,
LLDP_TLV_SYSTEM_DESCR = 6,
LLDP_TLV_SYSTEM_CAP = 7,
LLDP_TLV_MANAGEMENT_ADDR = 8,
LLDP_TLV_ORG = 127
};
enum {
LLDP_CHASSISID_SUBTYPE_CHASSIS = 1,
LLDP_CHASSISID_SUBTYPE_IFALIAS = 2,
LLDP_CHASSISID_SUBTYPE_PORT = 3,
LLDP_CHASSISID_SUBTYPE_LLADDR = 4,
LLDP_CHASSISID_SUBTYPE_ADDR = 5,
LLDP_CHASSISID_SUBTYPE_IFNAME = 6,
LLDP_CHASSISID_SUBTYPE_LOCAL = 7
};
enum {
LLDP_PORTID_SUBTYPE_IFALIAS = 1,
LLDP_PORTID_SUBTYPE_PORT = 2,
LLDP_PORTID_SUBTYPE_LLADDR = 3,
LLDP_PORTID_SUBTYPE_ADDR = 4,
LLDP_PORTID_SUBTYPE_IFNAME = 5,
LLDP_PORTID_SUBTYPE_AGENTCID = 6,
LLDP_PORTID_SUBTYPE_LOCAL = 7
};
#define LLDP_CAP_OTHER 0x01
#define LLDP_CAP_REPEATER 0x02
#define LLDP_CAP_BRIDGE 0x04
#define LLDP_CAP_WLAN 0x08
#define LLDP_CAP_ROUTER 0x10
#define LLDP_CAP_TELEPHONE 0x20
#define LLDP_CAP_DOCSIS 0x40
#define LLDP_CAP_STATION 0x80
#define LLDP_CAP_BITS \
"\20\01OTHER\02REPEATER\03BRIDGE\04WLAN\05ROUTER\06TELEPHONE" \
"\07DOCSIS\10STATION"
enum {
LLDP_MGMT_IFACE_UNKNOWN = 1,
LLDP_MGMT_IFACE_IFINDEX = 2,
LLDP_MGMT_IFACE_SYSPORT = 3
};
static const char *afnumber[] = AFNUM_NAME_STR;
void lldp_print_str(u_int8_t *, int);
const char *lldp_print_addr(int, const void *);
void lldp_print_id(int, u_int8_t *, int);
void
lldp_print_str(u_int8_t *str, int len)
{
int i;
printf("\"");
for (i = 0; i < len; i++)
printf("%c", isprint(str[i]) ? str[i] : '.');
printf("\"");
}
const char *
lldp_print_addr(int af, const void *addr)
{
static char buf[48];
if (inet_ntop(af, addr, buf, sizeof(buf)) == NULL)
return ("?");
return (buf);
}
void
lldp_print_id(int type, u_int8_t *ptr, int len)
{
u_int8_t id;
u_int8_t *data;
id = *(u_int8_t *)ptr;
len -= sizeof(u_int8_t);
data = ptr + sizeof(u_int8_t);
if (len <= 0)
return;
if (type == LLDP_TLV_CHASSIS_ID) {
switch (id) {
case LLDP_CHASSISID_SUBTYPE_CHASSIS:
printf("chassis ");
lldp_print_str(data, len);
break;
case LLDP_CHASSISID_SUBTYPE_IFALIAS:
printf("ifalias");
break;
case LLDP_CHASSISID_SUBTYPE_PORT:
printf("port");
break;
case LLDP_CHASSISID_SUBTYPE_LLADDR:
printf("lladdr %s",
ether_ntoa((struct ether_addr *)data));
break;
case LLDP_CHASSISID_SUBTYPE_ADDR:
printf("addr");
break;
case LLDP_CHASSISID_SUBTYPE_IFNAME:
printf("ifname ");
lldp_print_str(data, len);
break;
case LLDP_CHASSISID_SUBTYPE_LOCAL:
printf("local ");
lldp_print_str(data, len);
break;
default:
printf("unknown 0x%02x", id);
break;
}
} else if (type == LLDP_TLV_PORT_ID) {
switch (id) {
case LLDP_PORTID_SUBTYPE_IFALIAS:
printf("ifalias");
break;
case LLDP_PORTID_SUBTYPE_PORT:
printf("port");
break;
case LLDP_PORTID_SUBTYPE_LLADDR:
printf("lladdr %s",
ether_ntoa((struct ether_addr *)data));
break;
case LLDP_PORTID_SUBTYPE_ADDR:
printf("addr");
break;
case LLDP_PORTID_SUBTYPE_IFNAME:
printf("ifname ");
lldp_print_str(data, len);
break;
case LLDP_PORTID_SUBTYPE_AGENTCID:
printf("agentcid");
break;
case LLDP_PORTID_SUBTYPE_LOCAL:
printf("local ");
lldp_print_str(data, len);
break;
default:
printf("unknown 0x%02x", id);
break;
}
}
}
void
lldp_print(const u_char *p, u_int len)
{
u_int16_t tlv;
u_int8_t *ptr = (u_int8_t *)p, v = 0;
int n, type, vlen, alen;
printf("LLDP");
#define _ptrinc(_v) ptr += (_v); vlen -= (_v);
for (n = 0; n < len;) {
TCHECK2(*ptr, sizeof(tlv));
tlv = EXTRACT_16BITS(ptr);
type = (tlv & 0xfe00) >> 9;
vlen = tlv & 0x1ff;
n += vlen;
ptr += sizeof(tlv);
TCHECK2(*ptr, vlen);
switch (type) {
case LLDP_TLV_END:
goto done;
break;
case LLDP_TLV_CHASSIS_ID:
printf(", ChassisId: ");
lldp_print_id(type, ptr, vlen);
break;
case LLDP_TLV_PORT_ID:
printf(", PortId: ");
lldp_print_id(type, ptr, vlen);
break;
case LLDP_TLV_TTL:
printf(", TTL: ");
TCHECK2(*ptr, 2);
printf("%ds", EXTRACT_16BITS(ptr));
break;
case LLDP_TLV_PORT_DESCR:
printf(", PortDescr: ");
lldp_print_str(ptr, vlen);
break;
case LLDP_TLV_SYSTEM_NAME:
printf(", SysName: ");
lldp_print_str(ptr, vlen);
break;
case LLDP_TLV_SYSTEM_DESCR:
printf(", SysDescr: ");
lldp_print_str(ptr, vlen);
break;
case LLDP_TLV_SYSTEM_CAP:
printf(", CAP:");
TCHECK2(*ptr, 4);
printb(" available", EXTRACT_16BITS(ptr),
LLDP_CAP_BITS);
_ptrinc(sizeof(u_int16_t));
printb(" enabled", EXTRACT_16BITS(ptr),
LLDP_CAP_BITS);
break;
case LLDP_TLV_MANAGEMENT_ADDR:
printf(", MgmtAddr:");
TCHECK2(*ptr, 2);
alen = *ptr - sizeof(u_int8_t);
_ptrinc(sizeof(u_int8_t));
v = *ptr;
_ptrinc(sizeof(u_int8_t));
if (v < AFNUM_MAX)
printf(" %s", afnumber[v]);
else
printf(" type %d", v);
TCHECK2(*ptr, alen);
switch (v) {
case AFNUM_INET:
if (alen != sizeof(struct in_addr))
goto trunc;
printf(" %s",
lldp_print_addr(AF_INET, ptr));
break;
case AFNUM_INET6:
if (alen != sizeof(struct in6_addr))
goto trunc;
printf(" %s",
lldp_print_addr(AF_INET6, ptr));
break;
}
_ptrinc(alen);
v = *(u_int8_t *)ptr;
break;
case LLDP_TLV_ORG:
printf(", Org");
break;
default:
printf(", type %d length %d", type, vlen);
break;
}
ptr += vlen;
}
done:
return;
trunc:
printf(" [|LLDP]");
}
代码用于编译源代码的Makefile，
# build helloworld executable when user executes "make"
helloworld: helloworld.o
$(CC) $(LDFLAGS) helloworld.o -o helloworld
helloworld.o: helloworld.c
$(CC) $(CFLAGS) -c helloworld.c
# remove object files and executable when user executes "make clean"
clean:
rm *.o helloworld
但是，当我在文件夹make中运行命令~/helloworld/src$时，会出现以下错误。
cc helloworld.o -o helloworld
/usr/lib/gcc/x86_64-linux-gnu/4.6/../../../x86_64-linux-gnu/crt1.o: In function `_start':
(.text+0x20): undefined reference to `main'
helloworld.o: In function `lldp_print':
helloworld.c:(.text+0x36b): undefined reference to `snapend'
helloworld.c:(.text+0x376): undefined reference to `snapend'
helloworld.c:(.text+0x386): undefined reference to `snapend'
helloworld.c:(.text+0x3e3): undefined reference to `snapend'
helloworld.c:(.text+0x3f6): undefined reference to `snapend'
helloworld.o:helloworld.c:(.text+0x406): more undefined references to `snapend' follow
helloworld.o: In function `lldp_print':
helloworld.c:(.text+0x650): undefined reference to `printb'
helloworld.c:(.text+0x691): undefined reference to `printb'
helloworld.c:(.text+0x6af): undefined reference to `snapend'
helloworld.c:(.text+0x6ba): undefined reference to `snapend'
helloworld.c:(.text+0x6ca): undefined reference to `snapend'
helloworld.c:(.text+0x758): undefined reference to `snapend'
helloworld.c:(.text+0x76b): undefined reference to `snapend'
helloworld.o:helloworld.c:(.text+0x77b): more undefined references to `snapend' follow
collect2: ld returned 1 exit status
make: *** [helloworld] Error 1
我在Ubuntu中对C很新，并且真的会[[回复专家的建议如何让这段代码成功编译：）
再次感谢：）
答案 0 :(得分：0)
错误：
“主要”问题在第1条评论中进行了整理。
snapend在interface.h文件中定义，请确保将此文件与hallo.c放在同一目录中
printb函数在interface.h中声明，其源代码在util.c中。 因此，util.c也必须包含在你的makefile中。