Re: compile failed when using pcap, "undefined reference to `pcap_set_datalink"

["Arthur Chen" <iamarthur60 () hotmail com>]

Hi all,
   now I have found part of the error.
1) my system is redhat 9.0, and I installed pcap with these steps:
               root# ./configure
               root# ./make
               root# ./make install
  with these steps, in the Makefile's item 'install:', it showed out these 
things to do
          (a) copy libpcap.a to /usr/local/lib,
          (b)copy pcap.h, pcap-named.h pcap-bpf.h to /usr/local/include
2) It seems the 'configure' shell is wrong,
          (a) copy libpcap.a to /usr/local/lib,----this should be copy to 
/usr/lib
          (b)copy pcap.h, pcap-named.h pcap-bpf.h to 
/usr/local/include-----this is wrong, should be copy to /usr/include

3)But after I copied them to the correct place, I still can not compile, the 
error is still be:
"undefined reference to 'pcap_set_datalink'"
I have noticed that under the directory /usr/lib, there are several shared 
library files called libpcap.so, 
libpcap.so.0,libpcap.so.0.6,libpcap.so.0.6.2 , they might be the key 
problem---because when I make and instal the new PCAP library, I didn't see 
that there were any of these files be createdl:

----anybody help me!






> From: "Arthur Chen" <iamarthur60 () hotmail com>
> To: tcpdump-workers () tcpdump org
> Subject: [tcpdump-workers] small program compile failed when using pcap, 
> "undefined reference to `pcap_set"
> Date: Thu, 27 Nov 2003 23:00:02 +0000
>
> this small trying program can not compile, It said undefined reference to 
> `pcap_set_datalink', but this function prototype was included in pcap.h and 
> was implemented in pcap.c! Any idea?
>
>     This is the error message:
>
> [root@ arthur]# gcc -lpcap -o pcap_test.o pcap_test.c
> /tmp/ccViVFVU.o(.text+0xbb): In function `main':
> : undefined reference to `pcap_set_datalink'
> collect2: ld returned 1 exit status
> [root@ arthur]#
>
>
>      the source file is:
>
> #include <stdio.h>
> #include <pcap.h>
> //#include <pcap_int.h>
> extern int      pcap_set_datalink(pcap_t *, int);
>    int main()
>    {
>        pcap_t *handle;                       /* Session handle */
> //      char *dev;                            /* The device to sniff on */
>        char errbuf[PCAP_ERRBUF_SIZE];        /* Error string */
>        struct bpf_program filter;            /* The compiled filter */
> //      char filter_app[] = "port 23";        /* The filter expression */
>        char filter_app[] = "ether[11]=0xcb || (ether[5]=0xcb)";
>        bpf_u_int32 mask;                     /* Our netmask */
>        bpf_u_int32 net;                      /* Our IP */
>        struct pcap_pkthdr header;            /* The header that pcap gives 
> us */
>        const u_char *packet;                 /* The actual packet */
>        /* Define the device */
> //        dev = pcap_lookupdev(errbuf);
> char dev[]="eth0";
> int errCode=0;
>
> bpf_u_int32 counter=0;
> printf("the dev=%s\n",dev);
>
>        /* Find the properties for the device */
>        pcap_lookupnet(dev, &net, &mask, errbuf);
>         /* Open the session in promiscuous mode */
>        handle = pcap_open_live(dev, BUFSIZ, 1, 0, errbuf);
>         //printf("The data link is %d",(pcap_datalink(handle)));
> pcap_set_datalink(handle, DLT_PPP_ETHER);
>
> if (errCode)
>         printf("Set data link failed, error code=%d",errCode);
> else
>         printf("Set data link succeeded, ");
>
>         /* Compile and apply the filter */
> //        pcap_compile(handle, &filter, filter_app, 0, net);
>        pcap_compile(handle, &filter, filter_app, 0, net);
>         pcap_setfilter(handle, &filter);
>        /* Grab a packet */
>
>         packet = pcap_next(handle, &header);
>        /* Print its length */
>        printf("Jacked a packet with length of [%d]\n", header.len);
>        /* And close the session */
> for (; counter<header.len; counter++)
>         printf("%3x", *(packet+counter));
>
>         pcap_close(handle);
>
>        return(0);
>    }
>
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