source: libpacketdump/ip_17.cc @ 889ddc3

#include <stdio.h>
#include <inttypes.h>
#include <dlfcn.h>
#include <map>
#include "libpacketdump.h"
#include "libtrace.h"
#include <netinet/udp.h>
#include <netinet/in.h>
#include <netdb.h>

#define STRUCT udp

#define SAFE(x) \
        ((unsigned int)len>=((char*)&STRUCT->x-(char*)STRUCT+sizeof(STRUCT->x))) 
#define DISPLAY_EXP(x,fmt,exp) \
        if (SAFE(x)) \
                printf(fmt,exp); \
        else \
                return; 

#define DISPLAY(x,fmt) DISPLAY_EXP(x,fmt,STRUCT->x)

#define DISPLAYS(x,fmt) DISPLAY_EXP(x,fmt,htons(STRUCT->x))
#define DISPLAYL(x,fmt) DISPLAY_EXP(x,fmt,htonl(STRUCT->x))
#define DISPLAYIP(x,fmt) DISPLAY_EXP(x,fmt,inet_ntoa(*(struct in_addr*)&STRUCT->x))


extern "C"
void decode(int link_type,char *packet,int len)
{
        struct libtrace_udp *udp = (struct libtrace_udp*)packet;
        printf(" UDP:");
        if (SAFE(source)) {
                struct servent *ent=getservbyport(udp->source,"udp");
                if(ent) {
                        printf(" Source %i (%s)",htons(udp->source),ent->s_name);
                } else {
                        printf(" Source %i",htons(udp->source));
                }
        }
        else {
                printf("\n");
                return;
        }
        if (SAFE(dest)) {
                struct servent *ent=getservbyport(udp->dest,"udp");
                if(ent) {
                        printf(" Dest %i (%s)",htons(udp->dest),ent->s_name);
                } else {
                        printf(" Dest %i",htons(udp->dest));
                }
        }
        else {
                printf("\n");
                return;
        }
        printf("\n UDP:");
        DISPLAYS(len," Len %u");
        DISPLAYS(check," Checksum %u");
        printf("\n");
        if (htons(udp->source) < htons(udp->dest)) 
                decode_next(packet+sizeof(*udp),len-sizeof(*udp),"udp",htons(udp->source));
        else
                decode_next(packet+sizeof(*udp),len-sizeof(*udp),"udp",htons(udp->dest));
        return;
}