/* ------------------------------------------------------------------------- * libtcp-portmon.c: tcp port monitoring library. * * Copyright (C) 2005 Philip Kovacs kovacsp3@comcast.net * * This library is free software; you can redistribute it and/or * modify it under the terms of the GNU Lesser General Public * License as published by the Free Software Foundation; either * version 2.1 of the License, or (at your option) any later version. * * This library is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU * Lesser General Public License for more details. * * You should have received a copy of the GNU Lesser General Public * License along with this library; if not, write to the Free Software * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA * --------------------------------------------------------------------------- */ #include "libtcp-portmon.h" /* ------------------------------------------------------------------- * IMPLEMENTATION INTERFACE * * Implementation-specific interface begins here. Clients should not * manipulate these structures directly, nor call the defined helper * functions. Use the "Client interface" functions defined at bottom. * ------------------------------------------------------------------- */ /* ----------------------------------------------------------------------------- * Open-addressed hash implementation requires that we supply two hash functions * and a match function to compare two hash elements for identity. * ----------------------------------------------------------------------------- */ /* -------------------------------------------------- * Functions to hash the connections within a monitor * --------------------------------------------------*/ #define CONNECTION_HASH_KEY_LEN 17 /* ---------------------------------------------------------------------------------- * First connection hash function: DJB with a 65521 prime modulus to govern the range. * ----------------------------------------------------------------------------------*/ int connection_hash_function_1( const void *p_data ) { tcp_connection_t *p_conn; char key[CONNECTION_HASH_KEY_LEN]; unsigned int hash = 5381; unsigned int i = 0; if ( !p_data ) return -1; memset(key,0,sizeof(key)); /* p_data is a pointer to tcp_connection_t */ p_conn = (tcp_connection_t *)p_data; /* key is a hex representation of the connection */ snprintf(key, CONNECTION_HASH_KEY_LEN, "%08X%04X%04X", p_conn->remote_addr, p_conn->remote_port, p_conn->local_port); #ifdef HASH_DEBUG fprintf(stderr,"--- key=[%s]\n",key); #endif for(i = 0; i < CONNECTION_HASH_KEY_LEN-1; i++) { hash = ((hash << 5) + hash) + (key[i]); } return (hash & 0x7FFFFFFF) % 65521; } /* ------------------------------------------------------------------------- * Second connection hash function: DEK, modified to return odd numbers only, * as required for open-address hashing using double-hash probing. * Also uses a 65521 prime modulus to govern the range. * -------------------------------------------------------------------------*/ int connection_hash_function_2( const void *p_data ) { tcp_connection_t *p_conn; char key[CONNECTION_HASH_KEY_LEN]; unsigned int hash = CONNECTION_HASH_KEY_LEN-1; unsigned int i = 0; if ( !p_data ) return -1; memset(key,0,sizeof(key)); /* p_data is a pointer to a tcp_connection_t */ p_conn = (tcp_connection_t *)p_data; /* key is a hex representation of the connection */ snprintf(key, CONNECTION_HASH_KEY_LEN, "%08X%04X%04X", p_conn->remote_addr, p_conn->remote_port, p_conn->local_port); for(i = 0; i < CONNECTION_HASH_KEY_LEN-1; i++) { hash = ((hash << 5) ^ (hash >> 27)) ^ (key[i]); } return (( hash & 0x7FFFFFFF ) % 65521 ) | 0x00000001; } /* ------------------------------------------------------------------------- * Connection Match function returns non-zero if hash elements are identical. * -------------------------------------------------------------------------*/ int connection_match_function( const void *p_data1, const void *p_data2 ) { tcp_connection_t *p_conn1, *p_conn2; if ( !p_data1 || !p_data2 ) return 0; /* p_data1, p_data2 are pointers to tcp_connection_t */ p_conn1 = (tcp_connection_t *)p_data1; p_conn2 = (tcp_connection_t *)p_data2; return (p_conn1->local_addr == p_conn2->local_addr && p_conn1->local_port == p_conn2->local_port && p_conn1->remote_addr == p_conn2->remote_addr && p_conn1->remote_port == p_conn2->remote_port ); } /* -------------------------------------------------- * Functions to hash the monitors within a collection * --------------------------------------------------*/ #define MONITOR_HASH_KEY_LEN 9 /* ------------------------------------------------------------------------------- * First monitor hash function: DJB with a 65521 prime modulus to govern the range. * -------------------------------------------------------------------------------*/ int monitor_hash_function_1( const void *p_data ) { tcp_port_monitor_t *p_monitor; char key[MONITOR_HASH_KEY_LEN]; unsigned int hash = 5381; unsigned int i = 0; if ( !p_data ) return -1; memset(key,0,sizeof(key)); /* p_data is a pointer to tcp_port_monitor_t */ p_monitor = (tcp_port_monitor_t *)p_data; /* key is a hex representation of the starting port concatenated to the ending port */ snprintf(key, MONITOR_HASH_KEY_LEN, "%04X%04X", p_monitor->port_range_begin, p_monitor->port_range_end ); #ifdef HASH_DEBUG fprintf(stderr,"--- key=[%s]\n",key); #endif for(i = 0; i < MONITOR_HASH_KEY_LEN-1; i++) { hash = ((hash << 5) + hash) + (key[i]); } return (hash & 0x7FFFFFFF) % 65521; } /* ----------------------------------------------------------------------- * Second monitor hash function: DEK, modified to return odd numbers only, * as required for open-address hashing using double-hash probing. * Also uses a 65521 prime modulus to govern the range. * -----------------------------------------------------------------------*/ int monitor_hash_function_2( const void *p_data ) { tcp_port_monitor_t *p_monitor; char key[MONITOR_HASH_KEY_LEN]; unsigned int hash = MONITOR_HASH_KEY_LEN-1; unsigned int i = 0; if ( !p_data ) return -1; memset(key,0,sizeof(key)); /* p_data is a pointer to a tcp_port_monitor_t */ p_monitor = (tcp_port_monitor_t *)p_data; /* key is a hex representation of the starting port concatenated to the ending port */ snprintf(key, MONITOR_HASH_KEY_LEN, "%04X%04X", p_monitor->port_range_begin, p_monitor->port_range_end ); for(i = 0; i < MONITOR_HASH_KEY_LEN-1; i++) { hash = ((hash << 5) ^ (hash >> 27)) ^ (key[i]); } return (( hash & 0x7FFFFFFF ) % 65521 ) | 0x00000001; } /* ---------------------------------------------------------------------- * Monitor match function returns non-zero if hash elements are identical. * ----------------------------------------------------------------------*/ int monitor_match_function( const void *p_data1, const void *p_data2 ) { tcp_port_monitor_t *p_monitor1, *p_monitor2; if ( !p_data1 || !p_data2 ) return 0; /* p_data1, p_data2 are pointers to tcp_connection_t */ p_monitor1 = (tcp_port_monitor_t *)p_data1; p_monitor2 = (tcp_port_monitor_t *)p_data2; return (p_monitor1->port_range_begin == p_monitor1->port_range_begin && p_monitor2->port_range_end == p_monitor2->port_range_end); } /* --------------------------------------------------------------------------- * Port monitor utility functions implementing tcp_port_monitor_function_ptr_t * ---------------------------------------------------------------------------*/ void destroy_tcp_port_monitor( tcp_port_monitor_t * p_monitor, void * p_void ) { tcp_connection_node_t *p_node, *p_temp; if ( !p_monitor || p_void ) /* p_void should be NULL in this context */ return; /* destroy the monitor's hash */ hash_destroy(&p_monitor->hash); /* destroy the monitor's peek array */ free( p_monitor->p_peek ); /* destroy the monitor's connection list */ for ( p_node=p_monitor->connection_list.p_head; p_node!=NULL; ) { /* p_temp is for the next iteration */ p_temp = p_node->p_next; free( p_node ); p_node = p_temp; } /* destroy the monitor */ free( p_monitor ); } void age_tcp_port_monitor( tcp_port_monitor_t * p_monitor, void * p_void ) { /* Run through the monitor's connections and decrement the age variable. * If the age goes negative, we remove the connection from the monitor. * Function takes O(n) time on the number of connections. */ tcp_connection_node_t *p_node, *p_temp; tcp_connection_t *p_conn; void *p_cast; if ( !p_monitor || p_void ) /* p_void should be NULL in this context */ return; if ( !p_monitor->p_peek ) return; for ( p_node = p_monitor->connection_list.p_head; p_node != NULL; ) { if ( --p_node->connection.age >= 0 ) { p_node = p_node->p_next; continue; } /* connection on p_node is old. remove connection from the hash. */ p_conn = &p_node->connection; p_cast = (void *)p_conn; if ( hash_remove( &p_monitor->hash, &p_cast ) != 0 ) { #ifdef HASH_DEBUG fprintf(stderr, "--- hash_remove error\n"); #endif return; } /* splice p_node out of the connection_list */ if ( p_node->p_prev != NULL ) p_node->p_prev->p_next = p_node->p_next; if ( p_node->p_next != NULL ) p_node->p_next->p_prev = p_node->p_prev; /* correct the list head and tail if necessary */ if ( p_monitor->connection_list.p_head == p_node ) p_monitor->connection_list.p_head = p_node->p_next; if ( p_monitor->connection_list.p_tail == p_node ) p_monitor->connection_list.p_tail = p_node->p_prev; /* p_temp is for the next iteration */ p_temp = p_node->p_next; /* destroy the node */ free( p_node ); p_node = p_temp; } } void maintain_tcp_port_monitor_hash( tcp_port_monitor_t * p_monitor, void * p_void ) { /* Check the number of vacated slots in the hash. If it exceeds our maximum * threshold (should be about 1/4 of the hash table), then the hash table * performance degrades from O(1) toward O(n) as the number of vacated slots * climbs. This is avoided by clearing the hash and reinserting the entries. * The benefit of open-addressing hashing does come with this price -- * you must rebalance it occasionally. */ tcp_connection_node_t *p_node; double vacated_load; if ( !p_monitor || p_void ) /* p_void should be NULL in this context */ return; vacated_load = (double)p_monitor->hash.vacated / (double)p_monitor->hash.positions; #ifdef HASH_DEBUG fprintf(stderr,"--- num vacated is %d, vacated factor is %.3f\n", p_monitor->hash.vacated, vacated_load ); #endif if ( vacated_load <= TCP_CONNECIION_HASH_MAX_VACATED_PCT ) { /* hash is fine and needs no rebalancing */ return; } #ifdef HASH_DEBUG fprintf(stderr,"--- rebuilding hash\n"); #endif /* rebuild the hash */ memset( p_monitor->hash.pp_table, 0, p_monitor->hash.positions * sizeof(void **)); p_monitor->hash.size = 0; p_monitor->hash.vacated = 0; for ( p_node=p_monitor->connection_list.p_head; p_node!=NULL; p_node=p_node->p_next ) { if ( hash_insert( &p_monitor->hash, (void *)&p_node->connection ) != 0 ) { #ifdef HASH_DEBUG fprintf(stderr,"--- hash_insert error\n"); #endif ; } } } void rebuild_tcp_port_monitor_peek_table( tcp_port_monitor_t * p_monitor, void * p_void ) { /* Run through the monitori's connections and rebuild the peek table * of connection pointers. This is done so peeking into the monitor * can be done in O(1) time instead of O(n) time for each peek. */ tcp_connection_node_t *p_node; int i = 0; if ( !p_monitor || p_void ) /* p_void should be NULL in this context */ return; /* zero out the peek array */ memset( p_monitor->p_peek, 0, TCP_CONNECTION_HASH_SIZE * sizeof(tcp_connection_t *) ); for ( p_node=p_monitor->connection_list.p_head; p_node!=NULL; p_node=p_node->p_next, i++ ) { p_monitor->p_peek[i] = &p_node->connection; } } void show_connection_to_tcp_port_monitor( tcp_port_monitor_t * p_monitor, void * p_void ) { /* The monitor gets to look at each connection to see if it falls within * the monitor's port range of interest. Connections of interest are first * looked up in the hash to see if they are already there. If they are, we * reset the age of the connection so it is not deleted. If the connection * is not in the hash, we add it, but only if the hash is not saturated. * The function takes O(1) time. */ tcp_connection_node_t *p_node; void *p_cast; if ( !p_monitor || !p_void ) return; tcp_connection_t *p_connection = (tcp_connection_t *)p_void; /* inspect the local port number of the connection to see if we're interested. */ if ( (p_monitor->port_range_begin <= p_connection->local_port) && (p_connection->local_port <= p_monitor->port_range_end) ) { /* the connection is in the range of the monitor. */ /* first check the hash to see if the connection is already there. */ p_cast = (void *)p_connection; if ( hash_lookup( &p_monitor->hash, &p_cast ) == 0 ) { p_connection = (tcp_connection_t *)p_cast; /* it's already in the hash. reset the age of the connection. */ if ( p_connection != NULL ) { p_connection->age = TCP_CONNECIION_STARTING_AGE; } return; } /* Connection is not yet in the hash. We will try to add it, but only if the hash is not * yet saturated. We assume the hash is saturated (and therefore ignore this connection) * if our load factor cap is now exceeded. The benefit of limiting connections in this way * is that the hash will continue to function at an average (1) speed by keeping the load * load factor down. Of course the downside is that each port monitor has a strict maximum * connection limit. Future versions should probably allow the client to set the hash size * and load limits and/or provide for automatic resizing of hashes. */ if ( p_monitor->hash.size / p_monitor->hash.positions > TCP_CONNECTION_HASH_MAX_LOAD_PCT ) { /* hash exceeds our load limit is now "full" */ return; } /* create a new connection node */ if ( (p_node = (tcp_connection_node_t *) calloc(1, sizeof(tcp_connection_node_t))) == NULL ) return; p_node->connection = *p_connection; /* bitwise copy of the struct */ p_node->connection.age = TCP_CONNECIION_STARTING_AGE; p_node->p_next = NULL; /* insert it into the monitor's hash table */ if ( hash_insert( &p_monitor->hash, (void *)&p_node->connection ) != 0 ) { /* error inserting into hash. delete the connection node we just created, so no leaks. */ #ifdef HASH_DEBUG fprintf(stderr, "--- hash_insert error\n"); #endif free(p_node); return; } /* append the node to the monitor's connection list */ if ( p_monitor->connection_list.p_tail == NULL ) /* assume p_head is NULL too */ { p_monitor->connection_list.p_head = p_node; p_monitor->connection_list.p_tail = p_node; p_node->p_prev = NULL; } else { p_monitor->connection_list.p_tail->p_next = p_node; p_node->p_prev = p_monitor->connection_list.p_tail; p_monitor->connection_list.p_tail = p_node; } } } /* --------------------------------------------------------------------------------------- * Apply a tcp_port_monitor_function_ptr_t function to each port monitor in the collection. * ---------------------------------------------------------------------------------------*/ void for_each_tcp_port_monitor_in_collection( tcp_port_monitor_collection_t * p_collection, tcp_port_monitor_function_ptr_t p_function, void * p_function_args ) { tcp_port_monitor_node_t * p_current_node, * p_next_node; if ( !p_collection || !p_function ) return; /* for each monitor in the collection */ for ( p_current_node = p_collection->monitor_list.p_head; p_current_node != NULL; ) { p_next_node = p_current_node->p_next; /* do this first! */ if ( p_current_node->p_monitor ) { /* apply the function with the given arguments */ (*p_function)( p_current_node->p_monitor, p_function_args ); } p_current_node = p_next_node; } } /* ---------------------------------------------------------------------- * CLIENT INTERFACE * * Clients should call only those functions below this line. * ---------------------------------------------------------------------- */ /* ---------------------------------- * Client operations on port monitors * ---------------------------------- */ /* Clients should first try to "find_tcp_port_monitor" before creating one so that there are no redundant monitors. */ tcp_port_monitor_t * create_tcp_port_monitor( in_port_t port_range_begin, in_port_t port_range_end ) { tcp_port_monitor_t * p_monitor; /* create the monitor */ p_monitor = (tcp_port_monitor_t *) calloc(1, sizeof(tcp_port_monitor_t) ); if ( !p_monitor ) return NULL; /* create the monitor's connection hash */ if ( hash_create( &p_monitor->hash, TCP_CONNECTION_HASH_SIZE, &connection_hash_function_1, &connection_hash_function_2, &connection_match_function, NULL ) != 0 ) { /* we failed to create the hash, so destroy the monitor completely so we don't leak */ destroy_tcp_port_monitor(p_monitor,NULL); return NULL; } /* create the monitor's peek array */ if ( (p_monitor->p_peek = (tcp_connection_t **) calloc( TCP_CONNECTION_HASH_SIZE, sizeof(tcp_connection_t *))) == NULL ) { /* we failed to create the peek array, so destroy the monitor completely, again, so we don't leak */ destroy_tcp_port_monitor(p_monitor,NULL); return NULL ; } p_monitor->port_range_begin = port_range_begin; p_monitor->port_range_end = port_range_end; p_monitor->connection_list.p_head = NULL; p_monitor->connection_list.p_tail = NULL; return p_monitor; } /* Clients use this function to get connection data from the indicated port monitor. The requested monitor value is copied into a client-supplied char buffer. Returns 0 on success, -1 otherwise. */ int peek_tcp_port_monitor( tcp_port_monitor_t * p_monitor, int item, int connection_index, char * p_buffer, size_t buffer_size ) { struct hostent *p_hostent; struct servent *p_servent; struct in_addr net; if ( !p_monitor || !p_buffer || connection_index < 0 ) return(-1); memset(p_buffer, 0, buffer_size); memset(&net, 0, sizeof(net)); /* if the connection index is out of range, we simply return with no error * having first cleared the client-supplied buffer. */ if ( (item!=COUNT) && (connection_index > p_monitor->hash.size - 1) ) return(0); switch (item) { case COUNT: snprintf( p_buffer, buffer_size, "%d" , p_monitor->hash.size ); break; case REMOTEIP: net.s_addr = p_monitor->p_peek[ connection_index ]->remote_addr; snprintf( p_buffer, buffer_size, "%s", inet_ntoa( net ) ); break; case REMOTEHOST: p_hostent = gethostbyaddr( &p_monitor->p_peek[ connection_index ]->remote_addr, sizeof(in_addr_t), AF_INET); /* if no host name found, just use ip address. */ if ( !p_hostent || !p_hostent->h_name ) { net.s_addr = p_monitor->p_peek[ connection_index ]->remote_addr; snprintf( p_buffer, buffer_size, "%s", inet_ntoa( net ) ); break; } snprintf( p_buffer, buffer_size, "%s", p_hostent->h_name ); break; case REMOTEPORT: snprintf( p_buffer, buffer_size, "%d", p_monitor->p_peek[ connection_index ]->remote_port ); break; case LOCALIP: net.s_addr = p_monitor->p_peek[ connection_index ]->local_addr; snprintf( p_buffer, buffer_size, "%s", inet_ntoa( net ) ); break; case LOCALHOST: p_hostent = gethostbyaddr( &p_monitor->p_peek[ connection_index ]->local_addr, sizeof(in_addr_t), AF_INET); /* if no host name found, just use ip address. */ if ( !p_hostent || !p_hostent->h_name ) { net.s_addr = p_monitor->p_peek[ connection_index ]->local_addr; snprintf( p_buffer, buffer_size, "%s", inet_ntoa( net ) ); break; } snprintf( p_buffer, buffer_size, "%s", p_hostent->h_name ); break; case LOCALPORT: snprintf( p_buffer, buffer_size, "%d", p_monitor->p_peek[ connection_index ]->local_port ); break; case LOCALSERVICE: p_servent = getservbyport( htons(p_monitor->p_peek[ connection_index ]->local_port ), "tcp" ); /* if no service name found for the port, just use the port number. */ if ( !p_servent || !p_servent->s_name ) { snprintf( p_buffer, buffer_size, "%d", p_monitor->p_peek[ connection_index ]->local_port ); break; } snprintf( p_buffer, buffer_size, "%s", p_servent->s_name ); break; default: return(-1); } return(0); } /* -------------------------------- * Client operations on collections * -------------------------------- */ /* Create a monitor collection. Do this one first. */ tcp_port_monitor_collection_t * create_tcp_port_monitor_collection( void ) { tcp_port_monitor_collection_t * p_collection; p_collection = (tcp_port_monitor_collection_t *) calloc( 1, sizeof( tcp_port_monitor_collection_t ) ); if ( !p_collection ) return NULL; /* create the collection's monitor hash */ if ( hash_create( &p_collection->hash, TCP_MONITOR_HASH_SIZE, &monitor_hash_function_1, &monitor_hash_function_2, &monitor_match_function, NULL ) != 0 ) { /* we failed to create the hash, so destroy the monitor completely so we don't leak */ destroy_tcp_port_monitor_collection(p_collection); return NULL; } p_collection->monitor_list.p_head = NULL; p_collection->monitor_list.p_tail = NULL; return p_collection; } /* Destroy the monitor collection (and the monitors inside). Do this one last. */ void destroy_tcp_port_monitor_collection( tcp_port_monitor_collection_t * p_collection ) { tcp_port_monitor_node_t * p_current_node, * p_next_node; if ( !p_collection ) return; /* destroy the collection's hash */ hash_destroy( &p_collection->hash ); /* destroy the monitors */ for_each_tcp_port_monitor_in_collection( p_collection, &destroy_tcp_port_monitor, NULL ); /* next destroy the empty monitor nodes */ for ( p_current_node = p_collection->monitor_list.p_head; p_current_node != NULL; ) { p_next_node = p_current_node->p_next; /* do this first! */ free( p_current_node ); p_current_node = p_next_node; } free( p_collection ); } /* Updates the tcp statistics for all monitors within a collection */ void update_tcp_port_monitor_collection( tcp_port_monitor_collection_t * p_collection ) { FILE *fp; char buf[256]; tcp_connection_t conn; unsigned long state; if ( !p_collection ) return; /* age the connections in all port monitors. */ for_each_tcp_port_monitor_in_collection( p_collection, &age_tcp_port_monitor, NULL ); /* read tcp data from /proc/net/tcp */ if ( ( fp = fopen("/proc/net/tcp", "r" ) ) == NULL ) return; /* ignore field name line */ fgets(buf, 255, fp); /* read all tcp connections */ while (fgets (buf, sizeof (buf), fp) != NULL) { if ( sscanf (buf, "%*d: %lx:%lx %lx:%lx %lx %*x:%*x %*x:%*x %*x %lu %*d %lu", (unsigned long *)&conn.local_addr, (unsigned long *)&conn.local_port, (unsigned long *)&conn.remote_addr, (unsigned long *)&conn.remote_port, (unsigned long *)&state, (unsigned long *)&conn.uid, (unsigned long *)&conn.inode) != 7 ) fprintf( stderr, "/proc/net/tcp: bad file format\n" ); if ((conn.inode == 0) || (state != TCP_ESTABLISHED)) continue; /* show the connection to each port monitor. */ for_each_tcp_port_monitor_in_collection( p_collection, &show_connection_to_tcp_port_monitor, (void *) &conn ); } fclose(fp); /* check the health of the monitor hashes and rebuild them if nedded */ for_each_tcp_port_monitor_in_collection( p_collection, &maintain_tcp_port_monitor_hash, NULL ); /* rebuild the connection peek tables of all monitors so clients can peek in O(1) time */ for_each_tcp_port_monitor_in_collection( p_collection, &rebuild_tcp_port_monitor_peek_table, NULL ); } /* After clients create a monitor, use this to add it to the collection. Returns 0 on success, -1 otherwise. */ int insert_tcp_port_monitor_into_collection( tcp_port_monitor_collection_t * p_collection, tcp_port_monitor_t * p_monitor ) { tcp_port_monitor_node_t * p_node; if ( !p_collection || !p_monitor ) return (-1); /* create a container node for this monitor */ p_node = (tcp_port_monitor_node_t *) calloc( 1, sizeof(tcp_port_monitor_node_t) ); if ( !p_node ) return (-1); /* populate the node */ p_node->p_monitor = p_monitor; p_node->p_next = NULL; /* add a pointer to this monitor to the collection's hash */ if ( hash_insert( &p_collection->hash, (void *)p_monitor ) != 0 ) { /* error inserting into hash. destroy the monitor's container node so no leaks */ free( p_node ); return (-1); } /* tail of the container gets this node */ if ( !p_collection->monitor_list.p_tail ) p_collection->monitor_list.p_tail = p_node; else { /* p_next of the tail better be NULL */ if ( p_collection->monitor_list.p_tail->p_next != NULL ) return (-1); /* splice node onto tail */ p_collection->monitor_list.p_tail->p_next = p_node; p_collection->monitor_list.p_tail = p_node; } /* if this was the first element added */ if ( !p_collection->monitor_list.p_head ) p_collection->monitor_list.p_head = p_collection->monitor_list.p_tail; return 0; } /* Clients need a way to find monitors */ tcp_port_monitor_t * find_tcp_port_monitor( tcp_port_monitor_collection_t * p_collection, in_port_t port_range_begin, in_port_t port_range_end ) { tcp_port_monitor_t monitor,*p_monitor; void *p_cast; if ( !p_collection ) return NULL; /* need a monitor object to use for searching the hash */ monitor.port_range_begin = port_range_begin; monitor.port_range_end = port_range_end; p_monitor = &monitor; p_cast = (void *)p_monitor; /* simple hash table lookup */ if ( hash_lookup( &p_collection->hash, &p_cast ) == 0 ) { /* found the monitor and p_cast now points to it */ p_monitor = (tcp_port_monitor_t *)p_cast; return( p_monitor ); } return NULL; /* monitor not found */ }