1 files changed, 32 insertions, 48 deletions

diff --git a/net/ipv4/syncookies.c b/net/ipv4/syncookies.c
index 14a15c49129d..b95331e6c077 100644
--- a/net/ipv4/syncookies.c
+++ b/net/ipv4/syncookies.c
@@ -25,15 +25,7 @@
 
 extern int sysctl_tcp_syncookies;
 
-__u32 syncookie_secret[2][16-4+SHA_DIGEST_WORDS];
-EXPORT_SYMBOL(syncookie_secret);
-
-static __init int init_syncookies(void)
-{
-        get_random_bytes(syncookie_secret, sizeof(syncookie_secret));
-        return 0;
-}
-__initcall(init_syncookies);
+static u32 syncookie_secret[2][16-4+SHA_DIGEST_WORDS];
 
 #define COOKIEBITS 24   /* Upper bits store count */
 #define COOKIEMASK (((__u32)1 << COOKIEBITS) - 1)
@@ -44,8 +36,11 @@ static DEFINE_PER_CPU(__u32 [16 + 5 + SHA_WORKSPACE_WORDS],
 static u32 cookie_hash(__be32 saddr, __be32 daddr, __be16 sport, __be16 dport,
                        u32 count, int c)
 {
-        __u32 *tmp = __get_cpu_var(ipv4_cookie_scratch);
+        __u32 *tmp;
+
+        net_get_random_once(syncookie_secret, sizeof(syncookie_secret));
 
+        tmp  = __get_cpu_var(ipv4_cookie_scratch);
         memcpy(tmp + 4, syncookie_secret[c], sizeof(syncookie_secret[c]));
         tmp[0] = (__force u32)saddr;
         tmp[1] = (__force u32)daddr;
@@ -89,8 +84,7 @@ __u32 cookie_init_timestamp(struct request_sock *req)
 
 
 static __u32 secure_tcp_syn_cookie(__be32 saddr, __be32 daddr, __be16 sport,
-                                   __be16 dport, __u32 sseq, __u32 count,
-                                   __u32 data)
+                                   __be16 dport, __u32 sseq, __u32 data)
 {
         /*
          * Compute the secure sequence number.
@@ -102,7 +96,7 @@ static __u32 secure_tcp_syn_cookie(__be32 saddr, __be32 daddr, __be16 sport,
          * As an extra hack, we add a small "data" value that encodes the
          * MSS into the second hash value.
          */
-
+        u32 count = tcp_cookie_time();
         return (cookie_hash(saddr, daddr, sport, dport, 0, 0) +
                 sseq + (count << COOKIEBITS) +
                 ((cookie_hash(saddr, daddr, sport, dport, count, 1) + data)
@@ -114,22 +108,21 @@ static __u32 secure_tcp_syn_cookie(__be32 saddr, __be32 daddr, __be16 sport,
  * If the syncookie is bad, the data returned will be out of
  * range.  This must be checked by the caller.
  *
- * The count value used to generate the cookie must be within
- * "maxdiff" if the current (passed-in) "count".  The return value
- * is (__u32)-1 if this test fails.
+ * The count value used to generate the cookie must be less than
+ * MAX_SYNCOOKIE_AGE minutes in the past.
+ * The return value (__u32)-1 if this test fails.
  */
 static __u32 check_tcp_syn_cookie(__u32 cookie, __be32 saddr, __be32 daddr,
-                                  __be16 sport, __be16 dport, __u32 sseq,
-                                  __u32 count, __u32 maxdiff)
+                                  __be16 sport, __be16 dport, __u32 sseq)
 {
-        __u32 diff;
+        u32 diff, count = tcp_cookie_time();
 
         /* Strip away the layers from the cookie */
         cookie -= cookie_hash(saddr, daddr, sport, dport, 0, 0) + sseq;
 
         /* Cookie is now reduced to (count * 2^24) ^ (hash % 2^24) */
         diff = (count - (cookie >> COOKIEBITS)) & ((__u32) - 1 >> COOKIEBITS);
-        if (diff >= maxdiff)
+        if (diff >= MAX_SYNCOOKIE_AGE)
                 return (__u32)-1;
 
         return (cookie -
@@ -138,22 +131,22 @@ static __u32 check_tcp_syn_cookie(__u32 cookie, __be32 saddr, __be32 daddr,
 }
 
 /*
- * MSS Values are taken from the 2009 paper
- * 'Measuring TCP Maximum Segment Size' by S. Alcock and R. Nelson:
- *  - values 1440 to 1460 accounted for 80% of observed mss values
- *  - values outside the 536-1460 range are rare (<0.2%).
+ * MSS Values are chosen based on the 2011 paper
+ * 'An Analysis of TCP Maximum Segement Sizes' by S. Alcock and R. Nelson.
+ * Values ..
+ *  .. lower than 536 are rare (< 0.2%)
+ *  .. between 537 and 1299 account for less than < 1.5% of observed values
+ *  .. in the 1300-1349 range account for about 15 to 20% of observed mss values
+ *  .. exceeding 1460 are very rare (< 0.04%)
  *
- * Table must be sorted.
+ *  1460 is the single most frequently announced mss value (30 to 46% depending
+ *  on monitor location).  Table must be sorted.
  */
 static __u16 const msstab[] = {
-        64,
-        512,
         536,
-        1024,
-        1440,
+        1300,
+        1440,   /* 1440, 1452: PPPoE */
         1460,
-        4312,
-        8960,
 };
 
 /*
@@ -173,7 +166,7 @@ u32 __cookie_v4_init_sequence(const struct iphdr *iph, const struct tcphdr *th,
 
         return secure_tcp_syn_cookie(iph->saddr, iph->daddr,
                                      th->source, th->dest, ntohl(th->seq),
-                                     jiffies / (HZ * 60), mssind);
+                                     mssind);
 }
 EXPORT_SYMBOL_GPL(__cookie_v4_init_sequence);
 
@@ -189,13 +182,6 @@ __u32 cookie_v4_init_sequence(struct sock *sk, struct sk_buff *skb, __u16 *mssp)
 }
 
 /*
- * This (misnamed) value is the age of syncookie which is permitted.
- * Its ideal value should be dependent on TCP_TIMEOUT_INIT and
- * sysctl_tcp_retries1. It's a rather complicated formula (exponential
- * backoff) to compute at runtime so it's currently hardcoded here.
- */
-#define COUNTER_TRIES 4
-/*
  * Check if a ack sequence number is a valid syncookie.
  * Return the decoded mss if it is, or 0 if not.
  */
@@ -204,9 +190,7 @@ int __cookie_v4_check(const struct iphdr *iph, const struct tcphdr *th,
 {
         __u32 seq = ntohl(th->seq) - 1;
         __u32 mssind = check_tcp_syn_cookie(cookie, iph->saddr, iph->daddr,
-                                            th->source, th->dest, seq,
-                                            jiffies / (HZ * 60),
-                                            COUNTER_TRIES);
+                                            th->source, th->dest, seq);
 
         return mssind < ARRAY_SIZE(msstab) ? msstab[mssind] : 0;
 }
@@ -315,10 +299,10 @@ struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb,
         treq->rcv_isn           = ntohl(th->seq) - 1;
         treq->snt_isn           = cookie;
         req->mss                = mss;
-        ireq->loc_port          = th->dest;
-        ireq->rmt_port          = th->source;
-        ireq->loc_addr          = ip_hdr(skb)->daddr;
-        ireq->rmt_addr          = ip_hdr(skb)->saddr;
+        ireq->ir_num            = ntohs(th->dest);
+        ireq->ir_rmt_port       = th->source;
+        ireq->ir_loc_addr       = ip_hdr(skb)->daddr;
+        ireq->ir_rmt_addr       = ip_hdr(skb)->saddr;
         ireq->ecn_ok            = ecn_ok;
         ireq->snd_wscale        = tcp_opt.snd_wscale;
         ireq->sack_ok           = tcp_opt.sack_ok;
@@ -358,8 +342,8 @@ struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb,
         flowi4_init_output(&fl4, sk->sk_bound_dev_if, sk->sk_mark,
                            RT_CONN_FLAGS(sk), RT_SCOPE_UNIVERSE, IPPROTO_TCP,
                            inet_sk_flowi_flags(sk),
-                           (opt && opt->srr) ? opt->faddr : ireq->rmt_addr,
-                           ireq->loc_addr, th->source, th->dest);
+                           (opt && opt->srr) ? opt->faddr : ireq->ir_rmt_addr,
+                           ireq->ir_loc_addr, th->source, th->dest);
         security_req_classify_flow(req, flowi4_to_flowi(&fl4));
         rt = ip_route_output_key(sock_net(sk), &fl4);
         if (IS_ERR(rt)) {