I would like to filter and capture only SIP Packets using libpcap

[Apoo rva]

I am trying a code for packet capturing for only SIP traffic however I'm capturing other traffic also inspite of having setup a filter. The system I am working on is connected to a linux bridge. Please have a look @ the code and tell me what I am doing wrong

#include<pcap.h>
#include<stdlib.h>
#include<string.h>
#define MAXBYTES2CAPTURE 2074
 
void processPacket(u_char* arg,const struct pcap_pkthdr *pkthdr,const u_char *packet)
{
    int i=0,*counter=(int*)arg;
    printf("\nPacket count = %d",++(*counter));
    printf("\nrecieved packet size = %d",pkthdr->len);
    printf("\npayload\n");
    for(i=0;i<pkthdr->len;i++)
    {    if(isprint(packet[i]))
        printf("%c",packet[i]);
        else
        printf(". ");
        if(((i%16==0)&&(i!=0))||i==pkthdr->len-1)
        printf("\n");
    }
    return;
}
int main()
{
    int i=0,count=0;
    pcap_t *desc=NULL;
    char device[] = "my_bridge";
    char filter_exp[] = "port 5060";    /* The filter expression */
     bpf_u_int32 mask;        /* The netmask of our sniffing device */
     bpf_u_int32 net;        /* The IP of our sniffing device */
    char errbuf[PCAP_ERRBUF_SIZE];
    struct bpf_program fp;
    memset(errbuf,0,PCAP_ERRBUF_SIZE);
    if (pcap_lookupnet(device, &net, &mask, errbuf) == -1) {
         fprintf(stderr, "Can't get netmask for device %s\n", device);
         net = 0;
         mask = 0;
     }    
    printf("\nAfter looknet");
    printf("\nopening device %s",device);
    printf("\nnetmaskv 
",mask);
    printf("\nnet 
",net);
    desc=pcap_open_live(device,MAXBYTES2CAPTURE,1,512,errbuf);
    if (pcap_compile(desc, &fp, filter_exp, 1, net) == -1) {
         fprintf(stderr, "Couldn't parse filter %s: %s\n", filter_exp, pcap_geterr(desc));
         return(2);
     }
    else
    printf("\ncompile OK");
     if (pcap_setfilter(desc, &fp) == -1) {
         fprintf(stderr, "Couldn't install filter %s: %s\n", filter_exp, pcap_geterr(desc));
         return(2);
     }
    else printf("\nfilter ok");
    pcap_loop(desc,-1,processPacket,(u_char*)&count);
    return 0;
}