Determining clients IP address by service and PID

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Attached is a simple program that you may add to your collection of stuff for OSR5. I wrote this thing several years ago for use with a program where I needed to know a client's IP address, given the TCP service on which they were connected and the program's PID (to differentiate when more than one session was open on the same service). I recently cleaned it up so it could be used from the command line.

The command line syntax is:

    getrip <service> <PID>
 

where <service> is a TCP service defined in /etc/services (port numbers will not work) and <PID> is the process ID of a program that is serving a client attached to >service>. If both <service> and <PID> are found to be attached together, getrip will print the remote client's IP address to STDOUT and return 0 to the caller. Otherwise, getrip will return 1 to the caller and print suitable diagnostics to STDERR.

Example:

    getrip telnet 12345
 

A copyright statement will be displayed if you type what getrip. Invoking getrip with no arguments will display some help. Recommended perms are 755 and ownership should be bin:bin. The lsof utility must be present on the system and accessible in the execution environment.

source getrip.c
SCO coff getrip_coff
SCO ELF getrip

/*

get IP addr associated with port & PID -- 10/1999, wjb

grip port pid

remote IP printed on STDOUT

*/

#include <stdio.h>

#define S_BUF           192
#define S_IPADDR        15
#define S_PORT          16

char    *iam;

void    usage(void);

/*===========================================================================*/

void main(int argc,char *argv[]) {

    // argv[1] = port
    // argv[2] = caller's PID

        FILE    *f_lsof;
        char    *lsofcmd="lsof -n -T -w -i tcp:";
        int     bp=0;
        int     ip=0;
        int     oc;
        char    buffer[S_BUF+1];        // input buffer
        char    ipaddr[S_IPADDR+1];     // IP address

    iam=argv[0];

    if (argc != 3) {
        usage();
    };

    sprintf(buffer,"%s%s | grep %s | grep 0u",
        lsofcmd,argv[1],argv[2]);               // construct pipe command
    if ((f_lsof=popen(buffer,"r")) == NULL) {
        fprintf(stderr,"%s: couldn't pipe to lsof",iam);
        exit(1);
    };
    while ((oc=getc(f_lsof)) != EOF && (oc != '\n')) {
        *(buffer+bp++)=oc;
    };
    *(buffer+bp)=0;
    pclose(f_lsof);
    if (bp == 0) {
        fprintf(stderr,
            "%s: %s: no such process attached to %s\n",
            iam,argv[2],argv[1]);
        exit(1);
    };
    bp=0;
    while (*(buffer+bp)) {
        if (*(buffer+bp++) == '>') {
            while (*(buffer+bp)) {
                if (*(buffer+bp) == ':') {
                    *(ipaddr+ip)=0;
                    printf("%s\n",ipaddr);
                    exit(0);
                };
                *(ipaddr+ip++)=*(buffer+bp++);
            };
        };
    };
    fprintf(stderr,"%s: lsof output grabled: can't get IP address for %s\n",
        iam,argv[1]);
    exit(1);
}
/*===========================================================================*/

/* display usage help */

void usage(void) {
    fprintf(stderr,"usage: %s port PID\n\n",iam);
    fprintf(stderr,"%s%s%s%s%s%s%s",
        "    port  TCP port to interrogate, such as SMTP or POP3\n",
        "    PID   process ID of process bound to TCP port\n\n",
        "IP address, if any, is written to STDOUT.  Returns 0 if a matching\n",
        "IP address is found, 1 if not.\n\n",
        "The `lsof' utility must be installed on your system in order for\n",
        "this program to function.  `lsof' may be downloaded from SCO's\n",
        "Skunkware FTP site (ftp2.sco.com).\n");
    exit(1);
}
/*===========================================================================*/

/* copyright declaration for `what' command */

const char *what[]={
           "@(#)get remote IP address on TCP port V1.0 -- 10/16/1999",
           "@(#)                                  V1.1 -- 02/27/2004",
           "@(#)",
           "@(#)type `getrip' w/no arguments for command line usage",
           "@(#)",
           "@(#)Copyright (C)1985-2004 by BCS Technology Limited.  All rights",
           "@(#)reserved.  Permission granted to use, copy and/or  distribute",
           "@(#)this software,  providing proper attribution is given and all",
           "@(#)copyright notices remain intact.  This software is  *NOT*  in",
           "@(#)the public domain and has not been GPLed.",
           "@(#)",
           "@(#)!!! CAUTION:  USE AT YOUR OWN RISK !!!",
           "@(#)",
           "@(#)BCS Technology Limited does  not  accept  responsibility  for",
           "@(#)anything bad that might occur as a result of using this soft-",
           "@(#)ware.  Again, USE AT YOUR OWN RISK!",
           "@(#)"
        };
/*===========================================================================*/
 

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