url.c

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#include "evl.h"

/* Data structure for storing statistics on URLs*/

typedef struct Uc_Urls_t {
  Hash_t *urls; // key is text string, value is count
} Uc_Urls_t;

/**AutomaticStart */

// prototypes of static functions
static int Uc_UpdateUrls( Hash_t *, Pkt_ProcessPkt_t * );
static char* getUrl( char *, int );

/**AutomaticEnd */


/** \brief min function */

static int min( int a, int b ) { return ( ( a < b ) ? a : b ) ; }


/* \brief Code for keeping track of URLs */

int
urls (Evl_Manager_t * mgr, Pkt_ProcessPkt_t * pp, void **mystate, void *argument )
{
  Hash_t *urlHash = (Hash_t *) *mystate;

  if ( urlHash == NIL( Hash_t ) ) {
    urlHash = Hash_InitTable( strcmp, st_strhash );
    *mystate = urlHash;
  }
  Uc_UpdateUrls( urlHash, pp );

  return 0;
}


/** \brief Update urls */

static int 
Uc_UpdateUrls(
  Hash_t *hashPtr,
  Pkt_ProcessPkt_t *pp
)
{
  Pkt_IpHdr_t *ip = Pkt_EthernetExtractIp( pp->pkt );
  Pkt_TcpHdr_t *tcp = Pkt_IpExtractPayload (ip);
  char *payload = Pkt_TcpHdrReadPayload (tcp);
  int payloadLength = pp->length - ( ( (char *) payload ) - ( (char *) pp->pkt ) );
  char *url = getUrl( payload, payloadLength );
  if ( url == NIL( char ) ) {
    return 0;
  }
  int count;
  char tmpbuf[20];
  Pkt_PrintIpAddressDottedGeneral( tmpbuf, ip->destIp );
  char *fullUrl = util_strcat( tmpbuf,  url );
  free( url );
  url = fullUrl;
  if ( !Hash_Lookup( hashPtr, url, & count ) ) {
    Hash_Insert( hashPtr, url, 1 );
    printf("New url:%s\n", url );
  }
  else {
    count++;
    Hash_Insert( hashPtr, url, count );
    printf("Previously seen url with count %d:\t%s\n", count, url );
  }
  return 0;
}


/** \brief Extract the url from a string

*/

static char *getUrl(
  char *data,
  int length
)
{
  char *dup = malloc( length * sizeof( char )  );
  memcpy( dup, data, length );
  int i;
  char *start = "GET ";
  int startLen = strlen( start );
  char *anchor;
  for ( i = 0 ; i < length ; i++ ) {
    int N = min( startLen, length - i );
    if ( 0 == strncmp( start, dup + i, N ) ) {
      anchor = dup + i;
      break;
    }
  }
  if ( i == length ) {
    free( dup );
    return NIL( char );
  }
  char *urlStart =  anchor + startLen;
  char *urlEnd = dup + length;
  char buffer[2000];
  i = 0;
  while ( urlStart + i < urlEnd ) {
    if ( !isspace( *(urlStart + i) ) ) {
      buffer[i] = urlStart[i];
      i++;
    }
    else {
      buffer[i] = '\0';
      break;
    }
  }
  if ( urlStart + i == urlEnd ) {
    buffer[0] = '\0';
  }
  free( dup );
  return strdup( buffer );
}