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Diffstat (limited to 'net/ipv4/syncookies.c')
-rw-r--r--net/ipv4/syncookies.c80
1 files changed, 32 insertions, 48 deletions
diff --git a/net/ipv4/syncookies.c b/net/ipv4/syncookies.c
index 14a15c49129..b95331e6c07 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)) {
generated by cgit v1.2.3-18-g5258 (git 2.32.0) at 2024-12-27 17:46:15 +0000