/* * (C)opyright 1995 by Darren Reed. * * Redistribution and use in source and binary forms are permitted * provided that this notice is preserved and due credit is given * to the original author and the contributors. */ #if !defined(lint) && defined(LIBC_SCCS) static char sccsid[] = "@(#)ip_state.c 1.8 6/5/96 (C) 1993-1995 Darren Reed"; static char rcsid[] = "$Id: ip_state.c,v 1.1.1.3 1997/04/03 10:11:29 darrenr Exp $"; #endif #if !defined(_KERNEL) && !defined(KERNEL) # include # include #endif #include #include #include #include #include #if defined(__FreeBSD__) && (__FreeBSD__ >= 3) #include #include #include #else #include #endif #include #include #include #ifdef _KERNEL # include #endif #if !defined(__SVR4) && !defined(__svr4__) # include #else # include # include # include # include #endif #include #ifdef sun #include #endif #include #include #include #include #include #include #include #include #include #include #include "ip_compat.h" #include "ip_fil.h" #include "ip_state.h" #ifndef MIN #define MIN(a,b) (((a)<(b))?(a):(b)) #endif #define TCP_CLOSE (TH_FIN|TH_RST) ipstate_t *ips_table[IPSTATE_SIZE]; int ips_num = 0; ips_stat_t ips_stats; #if SOLARIS extern kmutex_t ipf_state; # if !defined(_KERNEL) #define bcopy(a,b,c) memmove(b,a,c) # endif #endif #define FIVE_DAYS (2 * 5 * 86400) /* 5 days: half closed session */ u_long fr_tcpidletimeout = FIVE_DAYS, fr_tcpclosewait = 60, fr_tcplastack = 20, fr_tcptimeout = 120, fr_tcpclosed = 1, fr_udptimeout = 120, fr_icmptimeout = 120; ips_stat_t *fr_statetstats() { ips_stats.iss_active = ips_num; ips_stats.iss_table = ips_table; return &ips_stats; } #define PAIRS(s1,d1,s2,d2) ((((s1) == (s2)) && ((d1) == (d2))) ||\ (((s1) == (d2)) && ((d1) == (s2)))) #define IPPAIR(s1,d1,s2,d2) PAIRS((s1).s_addr, (d1).s_addr, \ (s2).s_addr, (d2).s_addr) /* * Create a new ipstate structure and hang it off the hash table. */ int fr_addstate(ip, fin, pass) ip_t *ip; fr_info_t *fin; u_int pass; { ipstate_t ips; register ipstate_t *is = &ips; register u_int hv; if ((ip->ip_off & 0x1fff) || (fin->fin_fi.fi_fl & FI_SHORT)) return -1; if (ips_num == IPSTATE_MAX) { ips_stats.iss_max++; return -1; } ips.is_age = 1; ips.is_state[0] = 0; ips.is_state[1] = 0; /* * Copy and calculate... */ hv = (is->is_p = ip->ip_p); hv += (is->is_src.s_addr = ip->ip_src.s_addr); hv += (is->is_dst.s_addr = ip->ip_dst.s_addr); switch (ip->ip_p) { case IPPROTO_ICMP : { struct icmp *ic = (struct icmp *)fin->fin_dp; switch (ic->icmp_type) { case ICMP_ECHO : is->is_icmp.ics_type = 0; hv += (is->is_icmp.ics_id = ic->icmp_id); hv += (is->is_icmp.ics_seq = ic->icmp_seq); break; case ICMP_TSTAMP : case ICMP_IREQ : case ICMP_MASKREQ : is->is_icmp.ics_type = ic->icmp_type + 1; break; default : return -1; } ips_stats.iss_icmp++; is->is_age = fr_icmptimeout; break; } case IPPROTO_TCP : { register tcphdr_t *tcp = (tcphdr_t *)fin->fin_dp; /* * The endian of the ports doesn't matter, but the ack and * sequence numbers do as we do mathematics on them later. */ hv += (is->is_dport = tcp->th_dport); hv += (is->is_sport = tcp->th_sport); is->is_seq = ntohl(tcp->th_seq); is->is_ack = ntohl(tcp->th_ack); is->is_swin = ntohs(tcp->th_win); is->is_dwin = is->is_swin; /* start them the same */ ips_stats.iss_tcp++; /* * If we're creating state for a starting connectoin, start the * timer on it as we'll never see an error if it fails to * connect. */ if ((tcp->th_flags & (TH_SYN|TH_ACK)) == TH_SYN) is->is_ack = 0; /* Trumpet WinSock 'ism */ fr_tcp_age(&is->is_age, is->is_state, ip, fin, tcp->th_sport == is->is_sport); break; } case IPPROTO_UDP : { register tcphdr_t *tcp = (tcphdr_t *)fin->fin_dp; hv += (is->is_dport = tcp->th_dport); hv += (is->is_sport = tcp->th_sport); ips_stats.iss_udp++; is->is_age = fr_udptimeout; break; } default : return -1; } KMALLOC(is, ipstate_t *, sizeof(*is)); if (is == NULL) { ips_stats.iss_nomem++; return -1; } bcopy((char *)&ips, (char *)is, sizeof(*is)); hv %= IPSTATE_SIZE; MUTEX_ENTER(&ipf_state); is->is_next = ips_table[hv]; ips_table[hv] = is; is->is_pass = pass; is->is_pkts = 1; is->is_bytes = ip->ip_len; if (pass & FR_LOGFIRST) is->is_pass &= ~(FR_LOGFIRST|FR_LOG); ips_num++; #ifdef IPFILTER_LOG ipstate_log(is, ISL_NEW); #endif MUTEX_EXIT(&ipf_state); return 0; } /* * check to see if a packet with TCP headers fits within the TCP window. * change timeout depending on whether new packet is a SYN-ACK returning for a * SYN or a RST or FIN which indicate time to close up shop. */ int fr_tcpstate(is, fin, ip, tcp, sport) register ipstate_t *is; fr_info_t *fin; ip_t *ip; tcphdr_t *tcp; u_short sport; { register int seqskew, ackskew; register u_short swin, dwin; register tcp_seq seq, ack; int source; /* * Find difference between last checked packet and this packet. */ seq = ntohl(tcp->th_seq); ack = ntohl(tcp->th_ack); if (sport == is->is_sport) { seqskew = seq - is->is_seq; ackskew = ack - is->is_ack; } else { seqskew = ack - is->is_seq; if (!is->is_ack) /* * Must be a SYN-ACK in reply to a SYN. */ is->is_ack = seq; ackskew = seq - is->is_ack; } /* * Make skew values absolute */ if (seqskew < 0) seqskew = -seqskew; if (ackskew < 0) ackskew = -ackskew; /* * If the difference in sequence and ack numbers is within the * window size of the connection, store these values and match * the packet. */ if ((source = (sport == is->is_sport))) { swin = is->is_swin; dwin = is->is_dwin; } else { dwin = is->is_swin; swin = is->is_dwin; } if ((seqskew <= swin) && (ackskew <= dwin)) { if (source) { is->is_seq = seq; is->is_ack = ack; is->is_swin = ntohs(tcp->th_win); } else { is->is_seq = ack; is->is_ack = seq; is->is_dwin = ntohs(tcp->th_win); } ips_stats.iss_hits++; is->is_pkts++; is->is_bytes += ip->ip_len; /* * Nearing end of connection, start timeout. */ fr_tcp_age(&is->is_age, is->is_state, ip, fin, tcp->th_sport == is->is_sport); return 1; } return 0; } /* * Check if a packet has a registered state. */ int fr_checkstate(ip, fin) ip_t *ip; fr_info_t *fin; { register struct in_addr dst, src; register ipstate_t *is, **isp; register u_char pr; struct icmp *ic; tcphdr_t *tcp; u_int hv, hlen, pass; if ((ip->ip_off & 0x1fff) || (fin->fin_fi.fi_fl & FI_SHORT)) return 0; hlen = fin->fin_hlen; tcp = (tcphdr_t *)((char *)ip + hlen); ic = (struct icmp *)tcp; hv = (pr = ip->ip_p); hv += (src.s_addr = ip->ip_src.s_addr); hv += (dst.s_addr = ip->ip_dst.s_addr); /* * Search the hash table for matching packet header info. */ switch (ip->ip_p) { case IPPROTO_ICMP : hv += ic->icmp_id; hv += ic->icmp_seq; hv %= IPSTATE_SIZE; MUTEX_ENTER(&ipf_state); for (isp = &ips_table[hv]; (is = *isp); isp = &is->is_next) if ((is->is_p == pr) && (ic->icmp_id == is->is_icmp.ics_id) && (ic->icmp_seq == is->is_icmp.ics_seq) && IPPAIR(src, dst, is->is_src, is->is_dst)) { /* * If we have type 0 stored, allow any icmp * replies through. */ if (is->is_icmp.ics_type && is->is_icmp.ics_type != ic->icmp_type) continue; is->is_age = fr_icmptimeout; is->is_pkts++; is->is_bytes += ip->ip_len; ips_stats.iss_hits++; MUTEX_EXIT(&ipf_state); return is->is_pass; } MUTEX_EXIT(&ipf_state); break; case IPPROTO_TCP : { register u_short dport = tcp->th_dport, sport = tcp->th_sport; hv += dport; hv += sport; hv %= IPSTATE_SIZE; MUTEX_ENTER(&ipf_state); for (isp = &ips_table[hv]; (is = *isp); isp = &is->is_next) { if ((is->is_p == pr) && PAIRS(sport, dport, is->is_sport, is->is_dport) && IPPAIR(src, dst, is->is_src, is->is_dst)) if (fr_tcpstate(is, fin, ip, tcp, sport)) { #ifdef _KERNEL MUTEX_EXIT(&ipf_state); #else int pass = is->is_pass; if (tcp->th_flags & TCP_CLOSE) { *isp = is->is_next; isp = &ips_table[hv]; KFREE(is); } #endif return pass; } } MUTEX_EXIT(&ipf_state); break; } case IPPROTO_UDP : { register u_short dport = tcp->th_dport, sport = tcp->th_sport; hv += dport; hv += sport; hv %= IPSTATE_SIZE; /* * Nothing else to match on but ports. and IP#'s */ MUTEX_ENTER(&ipf_state); for (is = ips_table[hv]; is; is = is->is_next) if ((is->is_p == pr) && PAIRS(sport, dport, is->is_sport, is->is_dport) && IPPAIR(src, dst, is->is_src, is->is_dst)) { ips_stats.iss_hits++; is->is_pkts++; is->is_bytes += ip->ip_len; is->is_age = fr_udptimeout; pass = is->is_pass; MUTEX_EXIT(&ipf_state); return pass; } MUTEX_EXIT(&ipf_state); break; } default : break; } ips_stats.iss_miss++; return 0; } /* * Free memory in use by all state info. kept. */ void fr_stateunload() { register int i; register ipstate_t *is, **isp; int s; MUTEX_ENTER(&ipf_state); SPLNET(s); for (i = 0; i < IPSTATE_SIZE; i++) for (isp = &ips_table[i]; (is = *isp); ) { *isp = is->is_next; KFREE(is); } SPLX(s); MUTEX_EXIT(&ipf_state); } /* * Slowly expire held state for thingslike UDP and ICMP. Timeouts are set * in expectation of this being called twice per second. */ void fr_timeoutstate() { register int i; register ipstate_t *is, **isp; int s; MUTEX_ENTER(&ipf_state); SPLNET(s); for (i = 0; i < IPSTATE_SIZE; i++) for (isp = &ips_table[i]; (is = *isp); ) if (is->is_age && !--is->is_age) { *isp = is->is_next; if (is->is_p == IPPROTO_TCP) ips_stats.iss_fin++; else ips_stats.iss_expire++; #ifdef IPFILTER_LOG ipstate_log(is, ISL_EXPIRE); #endif KFREE(is); ips_num--; } else isp = &is->is_next; SPLX(s); MUTEX_EXIT(&ipf_state); } /* * Original idea freom Pradeep Krishnan for use primarily with NAT code. * (pkrishna@netcom.com) */ void fr_tcp_age(age, state, ip, fin, dir) u_long *age; u_char *state; ip_t *ip; fr_info_t *fin; int dir; { tcphdr_t *tcp = (tcphdr_t *)fin->fin_dp; u_char flags = tcp->th_flags; int dlen, ostate; ostate = state[1 - dir]; dlen = ip->ip_len - fin->fin_hlen - (tcp->th_off << 2); if (flags & TH_RST) { if (!(tcp->th_flags & TH_PUSH) && !dlen) { *age = fr_tcpclosed; state[dir] = TCPS_CLOSED; } else { *age = fr_tcpclosewait; state[dir] = TCPS_CLOSE_WAIT; } return; } *age = fr_tcptimeout; /* 1 min */ switch(state[dir]) { case TCPS_FIN_WAIT_2: case TCPS_CLOSED: if ((flags & TH_OPENING) == TH_OPENING) state[dir] = TCPS_SYN_RECEIVED; else if (flags & TH_SYN) state[dir] = TCPS_SYN_SENT; break; case TCPS_SYN_RECEIVED: if ((flags & (TH_FIN|TH_ACK)) == TH_ACK) { state[dir] = TCPS_ESTABLISHED; *age = fr_tcpidletimeout; } break; case TCPS_SYN_SENT: if ((flags & (TH_FIN|TH_ACK)) == TH_ACK) { state[dir] = TCPS_ESTABLISHED; *age = fr_tcpidletimeout; } break; case TCPS_ESTABLISHED: if (flags & TH_FIN) { state[dir] = TCPS_CLOSE_WAIT; if (!(flags & TH_PUSH) && !dlen && ostate > TCPS_ESTABLISHED) *age = fr_tcplastack; else *age = fr_tcpclosewait; } else *age = fr_tcpidletimeout; break; case TCPS_CLOSE_WAIT: if ((flags & TH_FIN) && !(flags & TH_PUSH) && !dlen && ostate > TCPS_ESTABLISHED) { *age = fr_tcplastack; state[dir] = TCPS_LAST_ACK; } else *age = fr_tcpclosewait; break; case TCPS_LAST_ACK: if (flags & TH_ACK) { state[dir] = TCPS_FIN_WAIT_2; if (!(flags & TH_PUSH) && !dlen && ostate > TCPS_ESTABLISHED) *age = fr_tcplastack; else { *age = fr_tcpclosewait; state[dir] = TCPS_CLOSE_WAIT; } } break; } } #ifdef IPFILTER_LOG void ipstate_log(is, type) struct ipstate *is; u_short type; { struct ipslog ipsl; if (iplused[IPL_LOGSTATE] + sizeof(ipsl) > IPLLOGSIZE) { ips_stats.iss_logfail++; return; } if (iplh[IPL_LOGSTATE] == iplbuf[IPL_LOGSTATE] + IPLLOGSIZE) iplh[IPL_LOGSTATE] = iplbuf[IPL_LOGSTATE]; # ifdef sun uniqtime(&ipsl); # endif # if BSD >= 199306 || defined(__FreeBSD__) microtime((struct timeval *)&ipsl); # endif ipsl.isl_pkts = is->is_pkts; ipsl.isl_bytes = is->is_bytes; ipsl.isl_src = is->is_src; ipsl.isl_dst = is->is_dst; ipsl.isl_p = is->is_p; ipsl.isl_flags = is->is_flags; ipsl.isl_type = type; if (ipsl.isl_p == IPPROTO_TCP || ipsl.isl_p == IPPROTO_UDP) { ipsl.isl_sport = is->is_sport; ipsl.isl_dport = is->is_dport; } else if (ipsl.isl_p == IPPROTO_ICMP) ipsl.isl_itype = is->is_icmp.ics_type; else { ipsl.isl_ps.isl_filler[0] = 0; ipsl.isl_ps.isl_filler[1] = 0; } if (!fr_copytolog(IPL_LOGSTATE, (char *)&ipsl, sizeof(ipsl))) { iplused[IPL_LOGSTATE] += sizeof(ipsl); ips_stats.iss_logged++; } else ips_stats.iss_logfail++; wakeup(iplbuf[IPL_LOGSTATE]); } #endif