TCPCT part 1g: Responder Cookie => Initiator
William Allen Simpson [Wed, 2 Dec 2009 18:25:27 +0000 (18:25 +0000)]
Parse incoming TCP_COOKIE option(s).

Calculate <SYN,ACK> TCP_COOKIE option.

Send optional <SYN,ACK> data.

This is a significantly revised implementation of an earlier (year-old)
patch that no longer applies cleanly, with permission of the original
author (Adam Langley):

    http://thread.gmane.org/gmane.linux.network/102586

Requires:
   TCPCT part 1a: add request_values parameter for sending SYNACK
   TCPCT part 1b: generate Responder Cookie secret
   TCPCT part 1c: sysctl_tcp_cookie_size, socket option TCP_COOKIE_TRANSACTIONS
   TCPCT part 1d: define TCP cookie option, extend existing struct's
   TCPCT part 1e: implement socket option TCP_COOKIE_TRANSACTIONS
   TCPCT part 1f: Initiator Cookie => Responder

Signed-off-by: William.Allen.Simpson@gmail.com
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/tcp.h
net/ipv4/syncookies.c
net/ipv4/tcp_input.c
net/ipv4/tcp_ipv4.c
net/ipv4/tcp_minisocks.c
net/ipv4/tcp_output.c
net/ipv6/syncookies.c
net/ipv6/tcp_ipv6.c

index f9abd9b..28b04ff 100644 (file)
@@ -407,6 +407,7 @@ extern int                  tcp_recvmsg(struct kiocb *iocb, struct sock *sk,
 
 extern void                    tcp_parse_options(struct sk_buff *skb,
                                                  struct tcp_options_received *opt_rx,
+                                                 u8 **hvpp,
                                                  int estab,
                                                  struct dst_entry *dst);
 
index 3146cc4..26399ad 100644 (file)
@@ -253,6 +253,8 @@ EXPORT_SYMBOL(cookie_check_timestamp);
 struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb,
                             struct ip_options *opt)
 {
+       struct tcp_options_received tcp_opt;
+       u8 *hash_location;
        struct inet_request_sock *ireq;
        struct tcp_request_sock *treq;
        struct tcp_sock *tp = tcp_sk(sk);
@@ -263,7 +265,6 @@ struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb,
        int mss;
        struct rtable *rt;
        __u8 rcv_wscale;
-       struct tcp_options_received tcp_opt;
 
        if (!sysctl_tcp_syncookies || !th->ack)
                goto out;
@@ -341,7 +342,7 @@ struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb,
 
        /* check for timestamp cookie support */
        memset(&tcp_opt, 0, sizeof(tcp_opt));
-       tcp_parse_options(skb, &tcp_opt, 0, &rt->u.dst);
+       tcp_parse_options(skb, &tcp_opt, &hash_location, 0, &rt->u.dst);
 
        if (tcp_opt.saw_tstamp)
                cookie_check_timestamp(&tcp_opt);
index be166e0..57ae96a 100644 (file)
@@ -3698,7 +3698,7 @@ old_ack:
  * the fast version below fails.
  */
 void tcp_parse_options(struct sk_buff *skb, struct tcp_options_received *opt_rx,
-                      int estab,  struct dst_entry *dst)
+                      u8 **hvpp, int estab,  struct dst_entry *dst)
 {
        unsigned char *ptr;
        struct tcphdr *th = tcp_hdr(skb);
@@ -3785,7 +3785,30 @@ void tcp_parse_options(struct sk_buff *skb, struct tcp_options_received *opt_rx,
                                 */
                                break;
 #endif
-                       }
+                       case TCPOPT_COOKIE:
+                               /* This option is variable length.
+                                */
+                               switch (opsize) {
+                               case TCPOLEN_COOKIE_BASE:
+                                       /* not yet implemented */
+                                       break;
+                               case TCPOLEN_COOKIE_PAIR:
+                                       /* not yet implemented */
+                                       break;
+                               case TCPOLEN_COOKIE_MIN+0:
+                               case TCPOLEN_COOKIE_MIN+2:
+                               case TCPOLEN_COOKIE_MIN+4:
+                               case TCPOLEN_COOKIE_MIN+6:
+                               case TCPOLEN_COOKIE_MAX:
+                                       /* 16-bit multiple */
+                                       opt_rx->cookie_plus = opsize;
+                                       *hvpp = ptr;
+                               default:
+                                       /* ignore option */
+                                       break;
+                               };
+                               break;
+                       };
 
                        ptr += opsize-2;
                        length -= opsize;
@@ -3813,17 +3836,20 @@ static int tcp_parse_aligned_timestamp(struct tcp_sock *tp, struct tcphdr *th)
  * If it is wrong it falls back on tcp_parse_options().
  */
 static int tcp_fast_parse_options(struct sk_buff *skb, struct tcphdr *th,
-                                 struct tcp_sock *tp)
+                                 struct tcp_sock *tp, u8 **hvpp)
 {
-       if (th->doff == sizeof(struct tcphdr) >> 2) {
+       /* In the spirit of fast parsing, compare doff directly to constant
+        * values.  Because equality is used, short doff can be ignored here.
+        */
+       if (th->doff == (sizeof(*th) / 4)) {
                tp->rx_opt.saw_tstamp = 0;
                return 0;
        } else if (tp->rx_opt.tstamp_ok &&
-                  th->doff == (sizeof(struct tcphdr)>>2)+(TCPOLEN_TSTAMP_ALIGNED>>2)) {
+                  th->doff == ((sizeof(*th) + TCPOLEN_TSTAMP_ALIGNED) / 4)) {
                if (tcp_parse_aligned_timestamp(tp, th))
                        return 1;
        }
-       tcp_parse_options(skb, &tp->rx_opt, 1, NULL);
+       tcp_parse_options(skb, &tp->rx_opt, hvpp, 1, NULL);
        return 1;
 }
 
@@ -5077,10 +5103,12 @@ out:
 static int tcp_validate_incoming(struct sock *sk, struct sk_buff *skb,
                              struct tcphdr *th, int syn_inerr)
 {
+       u8 *hash_location;
        struct tcp_sock *tp = tcp_sk(sk);
 
        /* RFC1323: H1. Apply PAWS check first. */
-       if (tcp_fast_parse_options(skb, th, tp) && tp->rx_opt.saw_tstamp &&
+       if (tcp_fast_parse_options(skb, th, tp, &hash_location) &&
+           tp->rx_opt.saw_tstamp &&
            tcp_paws_discard(sk, skb)) {
                if (!th->rst) {
                        NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_PAWSESTABREJECTED);
@@ -5368,12 +5396,14 @@ discard:
 static int tcp_rcv_synsent_state_process(struct sock *sk, struct sk_buff *skb,
                                         struct tcphdr *th, unsigned len)
 {
-       struct tcp_sock *tp = tcp_sk(sk);
+       u8 *hash_location;
        struct inet_connection_sock *icsk = inet_csk(sk);
-       int saved_clamp = tp->rx_opt.mss_clamp;
+       struct tcp_sock *tp = tcp_sk(sk);
        struct dst_entry *dst = __sk_dst_get(sk);
+       struct tcp_cookie_values *cvp = tp->cookie_values;
+       int saved_clamp = tp->rx_opt.mss_clamp;
 
-       tcp_parse_options(skb, &tp->rx_opt, 0, dst);
+       tcp_parse_options(skb, &tp->rx_opt, &hash_location, 0, dst);
 
        if (th->ack) {
                /* rfc793:
@@ -5470,6 +5500,31 @@ static int tcp_rcv_synsent_state_process(struct sock *sk, struct sk_buff *skb,
                 * Change state from SYN-SENT only after copied_seq
                 * is initialized. */
                tp->copied_seq = tp->rcv_nxt;
+
+               if (cvp != NULL &&
+                   cvp->cookie_pair_size > 0 &&
+                   tp->rx_opt.cookie_plus > 0) {
+                       int cookie_size = tp->rx_opt.cookie_plus
+                                       - TCPOLEN_COOKIE_BASE;
+                       int cookie_pair_size = cookie_size
+                                            + cvp->cookie_desired;
+
+                       /* A cookie extension option was sent and returned.
+                        * Note that each incoming SYNACK replaces the
+                        * Responder cookie.  The initial exchange is most
+                        * fragile, as protection against spoofing relies
+                        * entirely upon the sequence and timestamp (above).
+                        * This replacement strategy allows the correct pair to
+                        * pass through, while any others will be filtered via
+                        * Responder verification later.
+                        */
+                       if (sizeof(cvp->cookie_pair) >= cookie_pair_size) {
+                               memcpy(&cvp->cookie_pair[cvp->cookie_desired],
+                                      hash_location, cookie_size);
+                               cvp->cookie_pair_size = cookie_pair_size;
+                       }
+               }
+
                smp_mb();
                tcp_set_state(sk, TCP_ESTABLISHED);
 
index a2bcac9..59c911f 100644 (file)
@@ -1213,9 +1213,12 @@ static struct timewait_sock_ops tcp_timewait_sock_ops = {
 
 int tcp_v4_conn_request(struct sock *sk, struct sk_buff *skb)
 {
+       struct tcp_extend_values tmp_ext;
        struct tcp_options_received tmp_opt;
+       u8 *hash_location;
        struct request_sock *req;
        struct inet_request_sock *ireq;
+       struct tcp_sock *tp = tcp_sk(sk);
        struct dst_entry *dst = NULL;
        __be32 saddr = ip_hdr(skb)->saddr;
        __be32 daddr = ip_hdr(skb)->daddr;
@@ -1271,15 +1274,49 @@ int tcp_v4_conn_request(struct sock *sk, struct sk_buff *skb)
 
        tcp_clear_options(&tmp_opt);
        tmp_opt.mss_clamp = TCP_MSS_DEFAULT;
-       tmp_opt.user_mss  = tcp_sk(sk)->rx_opt.user_mss;
+       tmp_opt.user_mss  = tp->rx_opt.user_mss;
+       tcp_parse_options(skb, &tmp_opt, &hash_location, 0, dst);
+
+       if (tmp_opt.cookie_plus > 0 &&
+           tmp_opt.saw_tstamp &&
+           !tp->rx_opt.cookie_out_never &&
+           (sysctl_tcp_cookie_size > 0 ||
+            (tp->cookie_values != NULL &&
+             tp->cookie_values->cookie_desired > 0))) {
+               u8 *c;
+               u32 *mess = &tmp_ext.cookie_bakery[COOKIE_DIGEST_WORDS];
+               int l = tmp_opt.cookie_plus - TCPOLEN_COOKIE_BASE;
+
+               if (tcp_cookie_generator(&tmp_ext.cookie_bakery[0]) != 0)
+                       goto drop_and_release;
+
+               /* Secret recipe starts with IP addresses */
+               *mess++ ^= daddr;
+               *mess++ ^= saddr;
 
-       tcp_parse_options(skb, &tmp_opt, 0, dst);
+               /* plus variable length Initiator Cookie */
+               c = (u8 *)mess;
+               while (l-- > 0)
+                       *c++ ^= *hash_location++;
+
+#ifdef CONFIG_SYN_COOKIES
+               want_cookie = 0;        /* not our kind of cookie */
+#endif
+               tmp_ext.cookie_out_never = 0; /* false */
+               tmp_ext.cookie_plus = tmp_opt.cookie_plus;
+       } else if (!tp->rx_opt.cookie_in_always) {
+               /* redundant indications, but ensure initialization. */
+               tmp_ext.cookie_out_never = 1; /* true */
+               tmp_ext.cookie_plus = 0;
+       } else {
+               goto drop_and_release;
+       }
+       tmp_ext.cookie_in_always = tp->rx_opt.cookie_in_always;
 
        if (want_cookie && !tmp_opt.saw_tstamp)
                tcp_clear_options(&tmp_opt);
 
        tmp_opt.tstamp_ok = tmp_opt.saw_tstamp;
-
        tcp_openreq_init(req, &tmp_opt, skb);
 
        if (security_inet_conn_request(sk, skb, req))
@@ -1339,7 +1376,9 @@ int tcp_v4_conn_request(struct sock *sk, struct sk_buff *skb)
        }
        tcp_rsk(req)->snt_isn = isn;
 
-       if (__tcp_v4_send_synack(sk, dst, req, NULL) || want_cookie)
+       if (__tcp_v4_send_synack(sk, dst, req,
+                                (struct request_values *)&tmp_ext) ||
+           want_cookie)
                goto drop_and_free;
 
        inet_csk_reqsk_queue_hash_add(sk, req, TCP_TIMEOUT_INIT);
index 96852af..87accec 100644 (file)
@@ -90,13 +90,14 @@ enum tcp_tw_status
 tcp_timewait_state_process(struct inet_timewait_sock *tw, struct sk_buff *skb,
                           const struct tcphdr *th)
 {
-       struct tcp_timewait_sock *tcptw = tcp_twsk((struct sock *)tw);
        struct tcp_options_received tmp_opt;
+       u8 *hash_location;
+       struct tcp_timewait_sock *tcptw = tcp_twsk((struct sock *)tw);
        int paws_reject = 0;
 
        if (th->doff > (sizeof(*th) >> 2) && tcptw->tw_ts_recent_stamp) {
                tmp_opt.tstamp_ok = 1;
-               tcp_parse_options(skb, &tmp_opt, 1, NULL);
+               tcp_parse_options(skb, &tmp_opt, &hash_location, 1, NULL);
 
                if (tmp_opt.saw_tstamp) {
                        tmp_opt.ts_recent       = tcptw->tw_ts_recent;
@@ -518,15 +519,16 @@ struct sock *tcp_check_req(struct sock *sk, struct sk_buff *skb,
                           struct request_sock *req,
                           struct request_sock **prev)
 {
+       struct tcp_options_received tmp_opt;
+       u8 *hash_location;
+       struct sock *child;
        const struct tcphdr *th = tcp_hdr(skb);
        __be32 flg = tcp_flag_word(th) & (TCP_FLAG_RST|TCP_FLAG_SYN|TCP_FLAG_ACK);
        int paws_reject = 0;
-       struct tcp_options_received tmp_opt;
-       struct sock *child;
 
-       if ((th->doff > (sizeof(struct tcphdr)>>2)) && (req->ts_recent)) {
+       if ((th->doff > (sizeof(*th) >> 2)) && (req->ts_recent)) {
                tmp_opt.tstamp_ok = 1;
-               tcp_parse_options(skb, &tmp_opt, 1, NULL);
+               tcp_parse_options(skb, &tmp_opt, &hash_location, 1, NULL);
 
                if (tmp_opt.saw_tstamp) {
                        tmp_opt.ts_recent = req->ts_recent;
index 35dd983..2ac8bef 100644 (file)
@@ -655,48 +655,77 @@ static unsigned tcp_synack_options(struct sock *sk,
                                   struct request_sock *req,
                                   unsigned mss, struct sk_buff *skb,
                                   struct tcp_out_options *opts,
-                                  struct tcp_md5sig_key **md5) {
-       unsigned size = 0;
+                                  struct tcp_md5sig_key **md5,
+                                  struct tcp_extend_values *xvp)
+{
        struct inet_request_sock *ireq = inet_rsk(req);
-       char doing_ts;
+       unsigned remaining = MAX_TCP_OPTION_SPACE;
+       u8 cookie_plus = (xvp != NULL && !xvp->cookie_out_never) ?
+                        xvp->cookie_plus :
+                        0;
+       bool doing_ts = ireq->tstamp_ok;
 
 #ifdef CONFIG_TCP_MD5SIG
        *md5 = tcp_rsk(req)->af_specific->md5_lookup(sk, req);
        if (*md5) {
                opts->options |= OPTION_MD5;
-               size += TCPOLEN_MD5SIG_ALIGNED;
+               remaining -= TCPOLEN_MD5SIG_ALIGNED;
+
+               /* We can't fit any SACK blocks in a packet with MD5 + TS
+                * options. There was discussion about disabling SACK
+                * rather than TS in order to fit in better with old,
+                * buggy kernels, but that was deemed to be unnecessary.
+                */
+               doing_ts &= !ireq->sack_ok;
        }
 #else
        *md5 = NULL;
 #endif
 
-       /* we can't fit any SACK blocks in a packet with MD5 + TS
-          options. There was discussion about disabling SACK rather than TS in
-          order to fit in better with old, buggy kernels, but that was deemed
-          to be unnecessary. */
-       doing_ts = ireq->tstamp_ok && !(*md5 && ireq->sack_ok);
-
+       /* We always send an MSS option. */
        opts->mss = mss;
-       size += TCPOLEN_MSS_ALIGNED;
+       remaining -= TCPOLEN_MSS_ALIGNED;
 
        if (likely(ireq->wscale_ok)) {
                opts->ws = ireq->rcv_wscale;
                opts->options |= OPTION_WSCALE;
-               size += TCPOLEN_WSCALE_ALIGNED;
+               remaining -= TCPOLEN_WSCALE_ALIGNED;
        }
        if (likely(doing_ts)) {
                opts->options |= OPTION_TS;
                opts->tsval = TCP_SKB_CB(skb)->when;
                opts->tsecr = req->ts_recent;
-               size += TCPOLEN_TSTAMP_ALIGNED;
+               remaining -= TCPOLEN_TSTAMP_ALIGNED;
        }
        if (likely(ireq->sack_ok)) {
                opts->options |= OPTION_SACK_ADVERTISE;
                if (unlikely(!doing_ts))
-                       size += TCPOLEN_SACKPERM_ALIGNED;
+                       remaining -= TCPOLEN_SACKPERM_ALIGNED;
        }
 
-       return size;
+       /* Similar rationale to tcp_syn_options() applies here, too.
+        * If the <SYN> options fit, the same options should fit now!
+        */
+       if (*md5 == NULL &&
+           doing_ts &&
+           cookie_plus > TCPOLEN_COOKIE_BASE) {
+               int need = cookie_plus; /* has TCPOLEN_COOKIE_BASE */
+
+               if (0x2 & need) {
+                       /* 32-bit multiple */
+                       need += 2; /* NOPs */
+               }
+               if (need <= remaining) {
+                       opts->options |= OPTION_COOKIE_EXTENSION;
+                       opts->hash_size = cookie_plus - TCPOLEN_COOKIE_BASE;
+                       remaining -= need;
+               } else {
+                       /* There's no error return, so flag it. */
+                       xvp->cookie_out_never = 1; /* true */
+                       opts->hash_size = 0;
+               }
+       }
+       return MAX_TCP_OPTION_SPACE - remaining;
 }
 
 /* Compute TCP options for ESTABLISHED sockets. This is not the
@@ -2365,6 +2394,7 @@ struct sk_buff *tcp_make_synack(struct sock *sk, struct dst_entry *dst,
                                struct request_values *rvp)
 {
        struct tcp_out_options opts;
+       struct tcp_extend_values *xvp = tcp_xv(rvp);
        struct inet_request_sock *ireq = inet_rsk(req);
        struct tcp_sock *tp = tcp_sk(sk);
        struct tcphdr *th;
@@ -2408,8 +2438,8 @@ struct sk_buff *tcp_make_synack(struct sock *sk, struct dst_entry *dst,
 #endif
        TCP_SKB_CB(skb)->when = tcp_time_stamp;
        tcp_header_size = tcp_synack_options(sk, req, mss,
-                                            skb, &opts, &md5) +
-                         sizeof(struct tcphdr);
+                                            skb, &opts, &md5, xvp)
+                       + sizeof(*th);
 
        skb_push(skb, tcp_header_size);
        skb_reset_transport_header(skb);
@@ -2426,6 +2456,45 @@ struct sk_buff *tcp_make_synack(struct sock *sk, struct dst_entry *dst,
         */
        tcp_init_nondata_skb(skb, tcp_rsk(req)->snt_isn,
                             TCPCB_FLAG_SYN | TCPCB_FLAG_ACK);
+
+       if (OPTION_COOKIE_EXTENSION & opts.options) {
+               const struct tcp_cookie_values *cvp = tp->cookie_values;
+
+               if (cvp != NULL &&
+                   cvp->s_data_constant &&
+                   cvp->s_data_desired > 0) {
+                       u8 *buf = skb_put(skb, cvp->s_data_desired);
+
+                       /* copy data directly from the listening socket. */
+                       memcpy(buf, cvp->s_data_payload, cvp->s_data_desired);
+                       TCP_SKB_CB(skb)->end_seq += cvp->s_data_desired;
+               }
+
+               if (opts.hash_size > 0) {
+                       __u32 workspace[SHA_WORKSPACE_WORDS];
+                       u32 *mess = &xvp->cookie_bakery[COOKIE_DIGEST_WORDS];
+                       u32 *tail = &mess[COOKIE_MESSAGE_WORDS-1];
+
+                       /* Secret recipe depends on the Timestamp, (future)
+                        * Sequence and Acknowledgment Numbers, Initiator
+                        * Cookie, and others handled by IP variant caller.
+                        */
+                       *tail-- ^= opts.tsval;
+                       *tail-- ^= tcp_rsk(req)->rcv_isn + 1;
+                       *tail-- ^= TCP_SKB_CB(skb)->seq + 1;
+
+                       /* recommended */
+                       *tail-- ^= ((th->dest << 16) | th->source);
+                       *tail-- ^= (u32)cvp; /* per sockopt */
+
+                       sha_transform((__u32 *)&xvp->cookie_bakery[0],
+                                     (char *)mess,
+                                     &workspace[0]);
+                       opts.hash_location =
+                               (__u8 *)&xvp->cookie_bakery[0];
+               }
+       }
+
        th->seq = htonl(TCP_SKB_CB(skb)->seq);
        th->ack_seq = htonl(tcp_rsk(req)->rcv_isn + 1);
 
index 612fc53..5b9af50 100644 (file)
@@ -159,6 +159,8 @@ static inline int cookie_check(struct sk_buff *skb, __u32 cookie)
 
 struct sock *cookie_v6_check(struct sock *sk, struct sk_buff *skb)
 {
+       struct tcp_options_received tcp_opt;
+       u8 *hash_location;
        struct inet_request_sock *ireq;
        struct inet6_request_sock *ireq6;
        struct tcp_request_sock *treq;
@@ -171,7 +173,6 @@ struct sock *cookie_v6_check(struct sock *sk, struct sk_buff *skb)
        int mss;
        struct dst_entry *dst;
        __u8 rcv_wscale;
-       struct tcp_options_received tcp_opt;
 
        if (!sysctl_tcp_syncookies || !th->ack)
                goto out;
@@ -254,7 +255,7 @@ struct sock *cookie_v6_check(struct sock *sk, struct sk_buff *skb)
 
        /* check for timestamp cookie support */
        memset(&tcp_opt, 0, sizeof(tcp_opt));
-       tcp_parse_options(skb, &tcp_opt, 0, dst);
+       tcp_parse_options(skb, &tcp_opt, &hash_location, 0, dst);
 
        if (tcp_opt.saw_tstamp)
                cookie_check_timestamp(&tcp_opt);
index f2ec382..fc0a4e5 100644 (file)
@@ -1162,7 +1162,9 @@ static struct sock *tcp_v6_hnd_req(struct sock *sk,struct sk_buff *skb)
  */
 static int tcp_v6_conn_request(struct sock *sk, struct sk_buff *skb)
 {
+       struct tcp_extend_values tmp_ext;
        struct tcp_options_received tmp_opt;
+       u8 *hash_location;
        struct request_sock *req;
        struct inet6_request_sock *treq;
        struct ipv6_pinfo *np = inet6_sk(sk);
@@ -1206,8 +1208,52 @@ static int tcp_v6_conn_request(struct sock *sk, struct sk_buff *skb)
        tcp_clear_options(&tmp_opt);
        tmp_opt.mss_clamp = IPV6_MIN_MTU - sizeof(struct tcphdr) - sizeof(struct ipv6hdr);
        tmp_opt.user_mss = tp->rx_opt.user_mss;
+       tcp_parse_options(skb, &tmp_opt, &hash_location, 0, dst);
+
+       if (tmp_opt.cookie_plus > 0 &&
+           tmp_opt.saw_tstamp &&
+           !tp->rx_opt.cookie_out_never &&
+           (sysctl_tcp_cookie_size > 0 ||
+            (tp->cookie_values != NULL &&
+             tp->cookie_values->cookie_desired > 0))) {
+               u8 *c;
+               u32 *d;
+               u32 *mess = &tmp_ext.cookie_bakery[COOKIE_DIGEST_WORDS];
+               int l = tmp_opt.cookie_plus - TCPOLEN_COOKIE_BASE;
+
+               if (tcp_cookie_generator(&tmp_ext.cookie_bakery[0]) != 0)
+                       goto drop_and_free;
+
+               /* Secret recipe starts with IP addresses */
+               d = &ipv6_hdr(skb)->daddr.s6_addr32[0];
+               *mess++ ^= *d++;
+               *mess++ ^= *d++;
+               *mess++ ^= *d++;
+               *mess++ ^= *d++;
+               d = &ipv6_hdr(skb)->saddr.s6_addr32[0];
+               *mess++ ^= *d++;
+               *mess++ ^= *d++;
+               *mess++ ^= *d++;
+               *mess++ ^= *d++;
+
+               /* plus variable length Initiator Cookie */
+               c = (u8 *)mess;
+               while (l-- > 0)
+                       *c++ ^= *hash_location++;
 
-       tcp_parse_options(skb, &tmp_opt, 0, dst);
+#ifdef CONFIG_SYN_COOKIES
+               want_cookie = 0;        /* not our kind of cookie */
+#endif
+               tmp_ext.cookie_out_never = 0; /* false */
+               tmp_ext.cookie_plus = tmp_opt.cookie_plus;
+       } else if (!tp->rx_opt.cookie_in_always) {
+               /* redundant indications, but ensure initialization. */
+               tmp_ext.cookie_out_never = 1; /* true */
+               tmp_ext.cookie_plus = 0;
+       } else {
+               goto drop_and_free;
+       }
+       tmp_ext.cookie_in_always = tp->rx_opt.cookie_in_always;
 
        if (want_cookie && !tmp_opt.saw_tstamp)
                tcp_clear_options(&tmp_opt);
@@ -1244,7 +1290,9 @@ static int tcp_v6_conn_request(struct sock *sk, struct sk_buff *skb)
 
        security_inet_conn_request(sk, skb, req);
 
-       if (tcp_v6_send_synack(sk, req, NULL) || want_cookie)
+       if (tcp_v6_send_synack(sk, req,
+                              (struct request_values *)&tmp_ext) ||
+           want_cookie)
                goto drop_and_free;
 
        inet6_csk_reqsk_queue_hash_add(sk, req, TCP_TIMEOUT_INIT);