set mss, adjust checksum

[l2tpns.git] / l2tpns.c

diff --git a/l2tpns.c b/l2tpns.c
index 6d0ef96..732d7e8 100644 (file)
--- a/l2tpns.c
+++ b/l2tpns.c
@@ -4,7 +4,7 @@
 // Copyright (c) 2002 FireBrick (Andrews & Arnold Ltd / Watchfront Ltd) - GPL licenced
 // vim: sw=8 ts=8
 
 // Copyright (c) 2002 FireBrick (Andrews & Arnold Ltd / Watchfront Ltd) - GPL licenced
 // vim: sw=8 ts=8
 

-char const *cvs_id_l2tpns = "$Id: l2tpns.c,v 1.125 2005-08-29 11:24:31 bodea Exp $";
+char const *cvs_id_l2tpns = "$Id: l2tpns.c,v 1.136 2005-09-16 05:54:53 bodea Exp $";

 
 #include <arpa/inet.h>
 #include <assert.h>
 
 #include <arpa/inet.h>
 #include <assert.h>


@@ -75,6 +75,10 @@ static int syslog_log = 0;   // are we logging to syslog
 static FILE *log_stream = 0;   // file handle for direct logging (i.e. direct into file, not via syslog).
 uint32_t last_id = 0;          // Unique ID for radius accounting
 
 static FILE *log_stream = 0;   // file handle for direct logging (i.e. direct into file, not via syslog).
 uint32_t last_id = 0;          // Unique ID for radius accounting
 

+// calculated from config->l2tp_mtu
+uint16_t MRU = 0;              // PPP MRU
+uint16_t MSS = 0;              // TCP MSS
+

 struct cli_session_actions *cli_session_actions = NULL;        // Pending session changes requested by CLI
 struct cli_tunnel_actions *cli_tunnel_actions = NULL;  // Pending tunnel changes required by CLI
 
 struct cli_session_actions *cli_session_actions = NULL;        // Pending session changes requested by CLI
 struct cli_tunnel_actions *cli_tunnel_actions = NULL;  // Pending tunnel changes required by CLI
 


@@ -104,7 +108,8 @@ config_descriptt config_values[] = {
        CONFIG("log_file", log_filename, STRING),
        CONFIG("pid_file", pid_file, STRING),
        CONFIG("random_device", random_device, STRING),
        CONFIG("log_file", log_filename, STRING),
        CONFIG("pid_file", pid_file, STRING),
        CONFIG("random_device", random_device, STRING),

-       CONFIG("l2tp_secret", l2tpsecret, STRING),
+       CONFIG("l2tp_secret", l2tp_secret, STRING),
+       CONFIG("l2tp_mtu", l2tp_mtu, INT),

        CONFIG("ppp_restart_time", ppp_restart_time, INT),
        CONFIG("ppp_max_configure", ppp_max_configure, INT),
        CONFIG("ppp_max_failure", ppp_max_failure, INT),
        CONFIG("ppp_restart_time", ppp_restart_time, INT),
        CONFIG("ppp_max_configure", ppp_max_configure, INT),
        CONFIG("ppp_max_failure", ppp_max_failure, INT),


@@ -135,6 +140,7 @@ config_descriptt config_values[] = {
        CONFIG("packet_limit", max_packets, INT),
        CONFIG("cluster_address", cluster_address, IPv4),
        CONFIG("cluster_interface", cluster_interface, STRING),
        CONFIG("packet_limit", max_packets, INT),
        CONFIG("cluster_address", cluster_address, IPv4),
        CONFIG("cluster_interface", cluster_interface, STRING),

+       CONFIG("cluster_mcast_ttl", cluster_mcast_ttl, INT),

        CONFIG("cluster_hb_interval", cluster_hb_interval, INT),
        CONFIG("cluster_hb_timeout", cluster_hb_timeout, INT),
        CONFIG("cluster_master_min_adv", cluster_master_min_adv, INT),
        CONFIG("cluster_hb_interval", cluster_hb_interval, INT),
        CONFIG("cluster_hb_timeout", cluster_hb_timeout, INT),
        CONFIG("cluster_master_min_adv", cluster_master_min_adv, INT),


@@ -977,6 +983,61 @@ int tun_write(uint8_t * data, int size)
        return write(tunfd, data, size);
 }
 
        return write(tunfd, data, size);
 }
 

+// adjust tcp mss to avoid fragmentation (called only for tcp packets with syn set)
+void adjust_tcp_mss(sessionidt s, tunnelidt t, uint8_t *buf, int len, uint8_t *tcp)
+{
+       int d = (tcp[12] >> 4) * 4;
+       uint8_t *mss = 0;
+       uint8_t *opts;
+       uint8_t *data;
+       uint16_t orig;
+       uint32_t sum;
+
+       if ((tcp[13] & 0x3f) & ~(TCP_FLAG_SYN|TCP_FLAG_ACK)) // only want SYN and SYN,ACK
+               return;
+
+       if (tcp + d > buf + len) // short?
+               return;
+
+       opts = tcp + 20;
+       data = tcp + d;
+
+       while (opts < data)
+       {
+               if (*opts == 2 && opts[1] == 4) // mss option (2), length 4
+               {
+                       mss = opts + 2;
+                       if (mss + 2 > data) return; // short?
+                       break;
+               }
+
+               if (*opts == 0) return; // end of options
+               if (*opts == 1 || !opts[1]) // no op (one byte), or no length (prevent loop)
+                       opts++;
+               else
+                       opts += opts[1]; // skip over option
+       }
+
+       if (!mss) return; // not found
+       orig = ntohs(*(uint16_t *) mss);
+
+       if (orig <= MSS) return; // mss OK
+
+       LOG(5, s, t, "TCP: %s:%u -> %s:%u SYN%s, adjusted mss from %u to %u\n",
+               fmtaddr(*(in_addr_t *) (buf + 12), 0), ntohs(*(uint16_t *) tcp),
+               fmtaddr(*(in_addr_t *) (buf + 16), 1), ntohs(*(uint16_t *) (tcp + 2)),
+               (tcp[13] & TCP_FLAG_ACK) ? ",ACK" : "", orig, MSS);
+
+       // set mss
+       *(int16_t *) mss = MSS;
+
+       // adjust checksum (see rfc1141)
+       sum = orig + (~MSS & 0xffff);
+       sum += ntohs(*(uint16_t *) (tcp + 16));
+       sum = (sum & 0xffff) + (sum >> 16);
+       *(uint16_t *) (tcp + 16) = htons(sum);
+}
+

 // process outgoing (to tunnel) IP
 //
 static void processipout(uint8_t *buf, int len)
 // process outgoing (to tunnel) IP
 //
 static void processipout(uint8_t *buf, int len)


@@ -1084,6 +1145,14 @@ static void processipout(uint8_t *buf, int len)
        if (session[s].filter_out && !ip_filter(buf, len, session[s].filter_out - 1))
                return;
 
        if (session[s].filter_out && !ip_filter(buf, len, session[s].filter_out - 1))
                return;
 

+       // adjust MSS on SYN and SYN,ACK packets with options
+       if ((ntohs(*(uint16_t *) (buf + 6)) & 0x1fff) == 0 && buf[9] == IPPROTO_TCP) // first tcp fragment
+       {
+               int ihl = (buf[0] & 0xf) * 4; // length of IP header
+               if (len >= ihl + 20 && (buf[ihl + 13] & TCP_FLAG_SYN) && ((buf[ihl + 12] >> 4) > 5))
+                       adjust_tcp_mss(s, t, buf, len, buf + ihl);
+       }
+

        if (sp->tbf_out)
        {
                // Are we throttling this session?
        if (sp->tbf_out)
        {
                // Are we throttling this session?


@@ -1580,7 +1649,7 @@ void sessionshutdown(sessionidt s, char *reason, int result, int error)
 
 void sendipcp(sessionidt s, tunnelidt t)
 {
 
 void sendipcp(sessionidt s, tunnelidt t)
 {

-       uint8_t buf[MAXCONTROL];
+       uint8_t buf[MAXETHER];

        uint8_t *q;
 
        CSTAT(sendipcp);
        uint8_t *q;
 
        CSTAT(sendipcp);


@@ -1592,7 +1661,7 @@ void sendipcp(sessionidt s, tunnelidt t)
                session[s].unique_id = last_id;
        }
 
                session[s].unique_id = last_id;
        }
 

-       q = makeppp(buf,sizeof(buf), 0, 0, s, t, PPPIPCP);
+       q = makeppp(buf, sizeof(buf), 0, 0, s, t, PPPIPCP);

        if (!q) return;
 
        *q = ConfigReq;
        if (!q) return;
 
        *q = ConfigReq;


@@ -1609,13 +1678,13 @@ void sendipcp(sessionidt s, tunnelidt t)
 
 void sendipv6cp(sessionidt s, tunnelidt t)
 {
 
 void sendipv6cp(sessionidt s, tunnelidt t)
 {

-       uint8_t buf[MAXCONTROL];
+       uint8_t buf[MAXETHER];

        uint8_t *q;
 
        CSTAT(sendipv6cp);
        LOG(3, s, t, "IPV6CP: send ConfigReq\n");
 
        uint8_t *q;
 
        CSTAT(sendipv6cp);
        LOG(3, s, t, "IPV6CP: send ConfigReq\n");
 

-       q = makeppp(buf,sizeof(buf), 0, 0, s, t, PPPIPV6CP);
+       q = makeppp(buf, sizeof(buf), 0, 0, s, t, PPPIPV6CP);

        if (!q) return;
 
        *q = ConfigReq;
        if (!q) return;
 
        *q = ConfigReq;


@@ -1826,6 +1895,11 @@ void processudp(uint8_t *buf, int len, struct sockaddr_in *addr)
                return;
        }
        l -= (p - buf);
                return;
        }
        l -= (p - buf);

+
+       // used to time out old tunnels
+       if (t && tunnel[t].state == TUNNELOPEN)
+               tunnel[t].lastrec = time_now;
+

        if (*buf & 0x80)
        {                          // control
                uint16_t message = 0xFFFF;      // message type
        if (*buf & 0x80)
        {                          // control
                uint16_t message = 0xFFFF;      // message type


@@ -1913,9 +1987,6 @@ void processudp(uint8_t *buf, int len, struct sockaddr_in *addr)
                        return;
                }
 
                        return;
                }
 

-               // This is used to time out old tunnels
-               tunnel[t].lastrec = time_now;
-

                // check sequence of this message
                {
                        int skip = tunnel[t].window; // track how many in-window packets are still in queue
                // check sequence of this message
                {
                        int skip = tunnel[t].window; // track how many in-window packets are still in queue


@@ -2005,7 +2076,7 @@ void processudp(uint8_t *buf, int len, struct sockaddr_in *addr)
                                        uint16_t orig_len;
 
                                        // handle hidden AVPs
                                        uint16_t orig_len;
 
                                        // handle hidden AVPs

-                                       if (!*config->l2tpsecret)
+                                       if (!*config->l2tp_secret)

                                        {
                                                LOG(1, s, t, "Hidden AVP requested, but no L2TP secret.\n");
                                                fatal = flags;
                                        {
                                                LOG(1, s, t, "Hidden AVP requested, but no L2TP secret.\n");
                                                fatal = flags;


@@ -2378,7 +2449,7 @@ void processudp(uint8_t *buf, int len, struct sockaddr_in *addr)
                                        if (amagic == 0) amagic = time_now;
                                        session[s].magic = amagic; // set magic number
                                        session[s].l2tp_flags = aflags; // set flags received
                                        if (amagic == 0) amagic = time_now;
                                        session[s].magic = amagic; // set magic number
                                        session[s].l2tp_flags = aflags; // set flags received

-                                       session[s].mru = DEFAULT_MRU;
+                                       session[s].mru = PPPMTU; // default

                                        controlnull(t); // ack
 
                                        // start LCP
                                        controlnull(t); // ack
 
                                        // start LCP


@@ -2386,6 +2457,7 @@ void processudp(uint8_t *buf, int len, struct sockaddr_in *addr)
                                        sess_local[s].lcp.conf_sent = 1;
                                        sess_local[s].lcp.nak_sent = 0;
                                        sess_local[s].lcp_authtype = config->radius_authprefer;
                                        sess_local[s].lcp.conf_sent = 1;
                                        sess_local[s].lcp.nak_sent = 0;
                                        sess_local[s].lcp_authtype = config->radius_authprefer;

+                                       sess_local[s].ppp_mru = MRU;

                                        session[s].ppp.lcp = RequestSent;
                                        sendlcp(s, t);
 
                                        session[s].ppp.lcp = RequestSent;
                                        sendlcp(s, t);
 


@@ -2415,7 +2487,7 @@ void processudp(uint8_t *buf, int len, struct sockaddr_in *addr)
        }
        else
        {                          // data
        }
        else
        {                          // data

-               uint16_t prot;
+               uint16_t proto;

 
                LOG_HEX(5, "Receive Tunnel Data", p, l);
                if (l > 2 && p[0] == 0xFF && p[1] == 0x03)
 
                LOG_HEX(5, "Receive Tunnel Data", p, l);
                if (l > 2 && p[0] == 0xFF && p[1] == 0x03)


@@ -2431,12 +2503,12 @@ void processudp(uint8_t *buf, int len, struct sockaddr_in *addr)
                }
                if (*p & 1)
                {
                }
                if (*p & 1)
                {

-                       prot = *p++;
+                       proto = *p++;

                        l--;
                }
                else
                {
                        l--;
                }
                else
                {

-                       prot = ntohs(*(uint16_t *) p);
+                       proto = ntohs(*(uint16_t *) p);

                        p += 2;
                        l -= 2;
                }
                        p += 2;
                        l -= 2;
                }


@@ -2456,43 +2528,43 @@ void processudp(uint8_t *buf, int len, struct sockaddr_in *addr)
                        return;
                }
 
                        return;
                }
 

-               if (prot == PPPPAP)
+               if (proto == PPPPAP)

                {
                        session[s].last_packet = time_now;
                        if (!config->cluster_iam_master) { master_forward_packet(buf, len, addr->sin_addr.s_addr, addr->sin_port); return; }
                        processpap(s, t, p, l);
                }
                {
                        session[s].last_packet = time_now;
                        if (!config->cluster_iam_master) { master_forward_packet(buf, len, addr->sin_addr.s_addr, addr->sin_port); return; }
                        processpap(s, t, p, l);
                }

-               else if (prot == PPPCHAP)
+               else if (proto == PPPCHAP)

                {
                        session[s].last_packet = time_now;
                        if (!config->cluster_iam_master) { master_forward_packet(buf, len, addr->sin_addr.s_addr, addr->sin_port); return; }
                        processchap(s, t, p, l);
                }
                {
                        session[s].last_packet = time_now;
                        if (!config->cluster_iam_master) { master_forward_packet(buf, len, addr->sin_addr.s_addr, addr->sin_port); return; }
                        processchap(s, t, p, l);
                }

-               else if (prot == PPPLCP)
+               else if (proto == PPPLCP)

                {
                        session[s].last_packet = time_now;
                        if (!config->cluster_iam_master) { master_forward_packet(buf, len, addr->sin_addr.s_addr, addr->sin_port); return; }
                        processlcp(s, t, p, l);
                }
                {
                        session[s].last_packet = time_now;
                        if (!config->cluster_iam_master) { master_forward_packet(buf, len, addr->sin_addr.s_addr, addr->sin_port); return; }
                        processlcp(s, t, p, l);
                }

-               else if (prot == PPPIPCP)
+               else if (proto == PPPIPCP)

                {
                        session[s].last_packet = time_now;
                        if (!config->cluster_iam_master) { master_forward_packet(buf, len, addr->sin_addr.s_addr, addr->sin_port); return; }
                        processipcp(s, t, p, l);
                }
                {
                        session[s].last_packet = time_now;
                        if (!config->cluster_iam_master) { master_forward_packet(buf, len, addr->sin_addr.s_addr, addr->sin_port); return; }
                        processipcp(s, t, p, l);
                }

-               else if (prot == PPPIPV6CP)
+               else if (proto == PPPIPV6CP && config->ipv6_prefix.s6_addr[0])

                {
                        session[s].last_packet = time_now;
                        if (!config->cluster_iam_master) { master_forward_packet(buf, len, addr->sin_addr.s_addr, addr->sin_port); return; }
                        processipv6cp(s, t, p, l);
                }
                {
                        session[s].last_packet = time_now;
                        if (!config->cluster_iam_master) { master_forward_packet(buf, len, addr->sin_addr.s_addr, addr->sin_port); return; }
                        processipv6cp(s, t, p, l);
                }

-               else if (prot == PPPCCP)
+               else if (proto == PPPCCP)

                {
                        session[s].last_packet = time_now;
                        if (!config->cluster_iam_master) { master_forward_packet(buf, len, addr->sin_addr.s_addr, addr->sin_port); return; }
                        processccp(s, t, p, l);
                }
                {
                        session[s].last_packet = time_now;
                        if (!config->cluster_iam_master) { master_forward_packet(buf, len, addr->sin_addr.s_addr, addr->sin_port); return; }
                        processccp(s, t, p, l);
                }

-               else if (prot == PPPIP)
+               else if (proto == PPPIP)

                {
                        if (session[s].die)
                        {
                {
                        if (session[s].die)
                        {


@@ -2509,13 +2581,8 @@ void processudp(uint8_t *buf, int len, struct sockaddr_in *addr)
 
                        processipin(s, t, p, l);
                }
 
                        processipin(s, t, p, l);
                }

-               else if (prot == PPPIPV6)
+               else if (proto == PPPIPV6 && config->ipv6_prefix.s6_addr[0])

                {
                {

-                       if (!config->ipv6_prefix.s6_addr[0])
-                       {
-                               LOG(1, s, t, "IPv6 not configured; yet received IPv6 packet. Ignoring.\n");
-                               return;
-                       }

                        if (session[s].die)
                        {
                                LOG(4, s, t, "Session %d is closing.  Don't process PPP packets\n", s);
                        if (session[s].die)
                        {
                                LOG(4, s, t, "Session %d is closing.  Don't process PPP packets\n", s);


@@ -2531,10 +2598,36 @@ void processudp(uint8_t *buf, int len, struct sockaddr_in *addr)
 
                        processipv6in(s, t, p, l);
                }
 
                        processipv6in(s, t, p, l);
                }

+               else if (session[s].ppp.lcp == Opened)
+               {
+                       uint8_t buf[MAXETHER];
+                       uint8_t *q;
+                       int mru = session[s].mru;
+                       if (mru > sizeof(buf)) mru = sizeof(buf);
+
+                       l += 6;
+                       if (l > mru) l = mru;
+
+                       q = makeppp(buf, sizeof(buf), 0, 0, s, t, proto);
+                       if (!q) return;
+
+                       *q = CodeRej;
+                       *(q + 1) = ++sess_local[s].lcp_ident;
+                       *(uint16_t *)(q + 2) = l;
+                       *(uint16_t *)(q + 4) = htons(proto);
+                       memcpy(q + 6, p, l - 6);
+
+                       if (proto == PPPIPV6CP)
+                               LOG(3, s, t, "LCP: send ProtocolRej (IPV6CP: not configured)\n");
+                       else
+                               LOG(2, s, t, "LCP: sent ProtocolRej (0x%04X: unsupported)\n", proto);
+
+                       tunnelsend(buf, l + (q - buf), t);
+               }

                else
                {
                else
                {

-                       STAT(tunnel_rx_errors);
-                       LOG(1, s, t, "Unknown PPP protocol %04X\n", prot);
+                       LOG(2, s, t, "Unknown PPP protocol 0x%04X received in LCP %s state\n",
+                               proto, ppp_state(session[s].ppp.lcp));

                }
        }
 }
                }
        }
 }


@@ -2645,7 +2738,7 @@ static void regular_cleanups(double period)
                        }
                }
                // Send hello
                        }
                }
                // Send hello

-               if (tunnel[t].state == TUNNELOPEN && tunnel[t].lastrec < TIME + 600)
+               if (tunnel[t].state == TUNNELOPEN && (time_now - tunnel[t].lastrec) > 60)

                {
                        controlt *c = controlnew(6); // sending HELLO
                        controladd(c, 0, t); // send the message
                {
                        controlt *c = controlnew(6); // sending HELLO
                        controladd(c, 0, t); // send the message


@@ -2833,7 +2926,7 @@ static void regular_cleanups(double period)
                // No data in ECHO_TIMEOUT seconds, send LCP ECHO
                if (session[s].ppp.phase >= Establish && (time_now - session[s].last_packet >= ECHO_TIMEOUT))
                {
                // No data in ECHO_TIMEOUT seconds, send LCP ECHO
                if (session[s].ppp.phase >= Establish && (time_now - session[s].last_packet >= ECHO_TIMEOUT))
                {

-                       uint8_t b[MAXCONTROL] = {0};
+                       uint8_t b[MAXETHER];

 
                        uint8_t *q = makeppp(b, sizeof(b), 0, 0, s, session[s].tunnel, PPPLCP);
                        if (!q) continue;
 
                        uint8_t *q = makeppp(b, sizeof(b), 0, 0, s, session[s].tunnel, PPPLCP);
                        if (!q) continue;


@@ -3469,6 +3562,7 @@ static void initdata(int optdebug, char *optconfig)
        config->debug = optdebug;
        config->num_tbfs = MAXTBFS;
        config->rl_rate = 28; // 28kbps
        config->debug = optdebug;
        config->num_tbfs = MAXTBFS;
        config->rl_rate = 28; // 28kbps

+       config->cluster_mcast_ttl = 1;

        config->cluster_master_min_adv = 1;
        config->ppp_restart_time = 3;
        config->ppp_max_configure = 10;
        config->cluster_master_min_adv = 1;
        config->ppp_restart_time = 3;
        config->ppp_max_configure = 10;


@@ -4142,7 +4236,7 @@ static void build_chap_response(uint8_t *challenge, uint8_t id, uint16_t challen
        MD5_CTX ctx;
        *challenge_response = NULL;
 
        MD5_CTX ctx;
        *challenge_response = NULL;
 

-       if (!*config->l2tpsecret)
+       if (!*config->l2tp_secret)

        {
                LOG(0, 0, 0, "LNS requested CHAP authentication, but no l2tp secret is defined\n");
                return;
        {
                LOG(0, 0, 0, "LNS requested CHAP authentication, but no l2tp secret is defined\n");
                return;


@@ -4154,7 +4248,7 @@ static void build_chap_response(uint8_t *challenge, uint8_t id, uint16_t challen
 
        MD5_Init(&ctx);
        MD5_Update(&ctx, &id, 1);
 
        MD5_Init(&ctx);
        MD5_Update(&ctx, &id, 1);

-       MD5_Update(&ctx, config->l2tpsecret, strlen(config->l2tpsecret));
+       MD5_Update(&ctx, config->l2tp_secret, strlen(config->l2tp_secret));

        MD5_Update(&ctx, challenge, challenge_length);
        MD5_Final(*challenge_response, &ctx);
 
        MD5_Update(&ctx, challenge, challenge_length);
        MD5_Final(*challenge_response, &ctx);
 


@@ -4221,6 +4315,17 @@ static void update_config()
                setbuf(log_stream, NULL);
        }
 
                setbuf(log_stream, NULL);
        }
 

+#define L2TP_HDRS              (20+8+6+4)      // L2TP data encaptulation: ip + udp + l2tp (data) + ppp (inc hdlc)
+#define TCP_HDRS               (20+20)         // TCP encapsulation: ip + tcp
+
+       if (config->l2tp_mtu <= 0)              config->l2tp_mtu = PPPMTU;
+       else if (config->l2tp_mtu < MINMTU)     config->l2tp_mtu = MINMTU;
+       else if (config->l2tp_mtu > MAXMTU)     config->l2tp_mtu = MAXMTU;
+
+       // reset MRU/MSS globals
+       MRU = config->l2tp_mtu - L2TP_HDRS;
+       MSS = MRU - TCP_HDRS;
+

        // Update radius
        config->numradiusservers = 0;
        for (i = 0; i < MAXRADSERVER; i++)
        // Update radius
        config->numradiusservers = 0;
        for (i = 0; i < MAXRADSERVER; i++)


@@ -5119,7 +5224,7 @@ static void unhide_value(uint8_t *value, size_t len, uint16_t type, uint8_t *vec
        // Compute initial pad
        MD5_Init(&ctx);
        MD5_Update(&ctx, (unsigned char *) &m, 2);
        // Compute initial pad
        MD5_Init(&ctx);
        MD5_Update(&ctx, (unsigned char *) &m, 2);

-       MD5_Update(&ctx, config->l2tpsecret, strlen(config->l2tpsecret));
+       MD5_Update(&ctx, config->l2tp_secret, strlen(config->l2tp_secret));

        MD5_Update(&ctx, vector, vec_len);
        MD5_Final(digest, &ctx);
 
        MD5_Update(&ctx, vector, vec_len);
        MD5_Final(digest, &ctx);
 


@@ -5132,7 +5237,7 @@ static void unhide_value(uint8_t *value, size_t len, uint16_t type, uint8_t *vec
                if (d >= sizeof(digest))
                {
                        MD5_Init(&ctx);
                if (d >= sizeof(digest))
                {
                        MD5_Init(&ctx);

-                       MD5_Update(&ctx, config->l2tpsecret, strlen(config->l2tpsecret));
+                       MD5_Update(&ctx, config->l2tp_secret, strlen(config->l2tp_secret));

                        MD5_Update(&ctx, last, sizeof(digest));
                        MD5_Final(digest, &ctx);
 
                        MD5_Update(&ctx, last, sizeof(digest));
                        MD5_Final(digest, &ctx);