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-rw-r--r--net/ipv4/syncookies.c89
-rw-r--r--net/ipv4/tcp_ipv4.c5
-rw-r--r--net/ipv4/tcp_output.c6
-rw-r--r--net/ipv6/syncookies.c20
-rw-r--r--net/ipv6/tcp_ipv6.c5
5 files changed, 109 insertions, 16 deletions
diff --git a/net/ipv4/syncookies.c b/net/ipv4/syncookies.c
index abc752d45cf..73ba98921d6 100644
--- a/net/ipv4/syncookies.c
+++ b/net/ipv4/syncookies.c
@@ -19,6 +19,10 @@
#include <linux/kernel.h>
#include <net/tcp.h>
+/* Timestamps: lowest 9 bits store TCP options */
+#define TSBITS 9
+#define TSMASK (((__u32)1 << TSBITS) - 1)
+
extern int sysctl_tcp_syncookies;
__u32 syncookie_secret[2][16-4+SHA_DIGEST_WORDS];
@@ -51,6 +55,39 @@ static u32 cookie_hash(__be32 saddr, __be32 daddr, __be16 sport, __be16 dport,
return tmp[17];
}
+
+/*
+ * when syncookies are in effect and tcp timestamps are enabled we encode
+ * tcp options in the lowest 9 bits of the timestamp value that will be
+ * sent in the syn-ack.
+ * Since subsequent timestamps use the normal tcp_time_stamp value, we
+ * must make sure that the resulting initial timestamp is <= tcp_time_stamp.
+ */
+__u32 cookie_init_timestamp(struct request_sock *req)
+{
+ struct inet_request_sock *ireq;
+ u32 ts, ts_now = tcp_time_stamp;
+ u32 options = 0;
+
+ ireq = inet_rsk(req);
+ if (ireq->wscale_ok) {
+ options = ireq->snd_wscale;
+ options |= ireq->rcv_wscale << 4;
+ }
+ options |= ireq->sack_ok << 8;
+
+ ts = ts_now & ~TSMASK;
+ ts |= options;
+ if (ts > ts_now) {
+ ts >>= TSBITS;
+ ts--;
+ ts <<= TSBITS;
+ ts |= options;
+ }
+ return ts;
+}
+
+
static __u32 secure_tcp_syn_cookie(__be32 saddr, __be32 daddr, __be16 sport,
__be16 dport, __u32 sseq, __u32 count,
__u32 data)
@@ -185,6 +222,35 @@ static inline struct sock *get_cookie_sock(struct sock *sk, struct sk_buff *skb,
return child;
}
+
+/*
+ * when syncookies are in effect and tcp timestamps are enabled we stored
+ * additional tcp options in the timestamp.
+ * This extracts these options from the timestamp echo.
+ *
+ * The lowest 4 bits are for snd_wscale
+ * The next 4 lsb are for rcv_wscale
+ * The next lsb is for sack_ok
+ */
+void cookie_check_timestamp(struct tcp_options_received *tcp_opt)
+{
+ /* echoed timestamp, 9 lowest bits contain options */
+ u32 options = tcp_opt->rcv_tsecr & TSMASK;
+
+ tcp_opt->snd_wscale = options & 0xf;
+ options >>= 4;
+ tcp_opt->rcv_wscale = options & 0xf;
+
+ tcp_opt->sack_ok = (options >> 4) & 0x1;
+
+ if (tcp_opt->sack_ok)
+ tcp_sack_reset(tcp_opt);
+
+ if (tcp_opt->snd_wscale || tcp_opt->rcv_wscale)
+ tcp_opt->wscale_ok = 1;
+}
+EXPORT_SYMBOL(cookie_check_timestamp);
+
struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb,
struct ip_options *opt)
{
@@ -198,6 +264,7 @@ 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;
@@ -210,6 +277,13 @@ struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb,
NET_INC_STATS_BH(LINUX_MIB_SYNCOOKIESRECV);
+ /* check for timestamp cookie support */
+ memset(&tcp_opt, 0, sizeof(tcp_opt));
+ tcp_parse_options(skb, &tcp_opt, 0);
+
+ if (tcp_opt.saw_tstamp)
+ cookie_check_timestamp(&tcp_opt);
+
ret = NULL;
req = reqsk_alloc(&tcp_request_sock_ops); /* for safety */
if (!req)
@@ -228,6 +302,12 @@ struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb,
ireq->loc_addr = ip_hdr(skb)->daddr;
ireq->rmt_addr = ip_hdr(skb)->saddr;
ireq->opt = NULL;
+ ireq->snd_wscale = tcp_opt.snd_wscale;
+ ireq->rcv_wscale = tcp_opt.rcv_wscale;
+ ireq->sack_ok = tcp_opt.sack_ok;
+ ireq->wscale_ok = tcp_opt.wscale_ok;
+ ireq->tstamp_ok = tcp_opt.saw_tstamp;
+ req->ts_recent = tcp_opt.saw_tstamp ? tcp_opt.rcv_tsval : 0;
/* We throwed the options of the initial SYN away, so we hope
* the ACK carries the same options again (see RFC1122 4.2.3.8)
@@ -242,8 +322,6 @@ struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb,
}
}
- ireq->snd_wscale = ireq->rcv_wscale = ireq->tstamp_ok = 0;
- ireq->wscale_ok = ireq->sack_ok = 0;
req->expires = 0UL;
req->retrans = 0;
@@ -272,11 +350,12 @@ struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb,
}
/* Try to redo what tcp_v4_send_synack did. */
- req->window_clamp = dst_metric(&rt->u.dst, RTAX_WINDOW);
+ req->window_clamp = tp->window_clamp ? :dst_metric(&rt->u.dst, RTAX_WINDOW);
+
tcp_select_initial_window(tcp_full_space(sk), req->mss,
&req->rcv_wnd, &req->window_clamp,
- 0, &rcv_wscale);
- /* BTW win scale with syncookies is 0 by definition */
+ ireq->wscale_ok, &rcv_wscale);
+
ireq->rcv_wscale = rcv_wscale;
ret = get_cookie_sock(sk, skb, req, &rt->u.dst);
diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index df89a566a5a..52e3ae603ca 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -1299,10 +1299,8 @@ int tcp_v4_conn_request(struct sock *sk, struct sk_buff *skb)
tcp_parse_options(skb, &tmp_opt, 0);
- if (want_cookie) {
+ if (want_cookie && !tmp_opt.saw_tstamp)
tcp_clear_options(&tmp_opt);
- tmp_opt.saw_tstamp = 0;
- }
if (tmp_opt.saw_tstamp && !tmp_opt.rcv_tsval) {
/* Some OSes (unknown ones, but I see them on web server, which
@@ -1330,6 +1328,7 @@ int tcp_v4_conn_request(struct sock *sk, struct sk_buff *skb)
if (want_cookie) {
#ifdef CONFIG_SYN_COOKIES
syn_flood_warning(skb);
+ req->cookie_ts = tmp_opt.tstamp_ok;
#endif
isn = cookie_v4_init_sequence(sk, skb, &req->mss);
} else if (!isn) {
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index a627616314b..76b3653e9b4 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -2233,7 +2233,11 @@ struct sk_buff *tcp_make_synack(struct sock *sk, struct dst_entry *dst,
/* RFC1323: The window in SYN & SYN/ACK segments is never scaled. */
th->window = htons(min(req->rcv_wnd, 65535U));
-
+#ifdef CONFIG_SYN_COOKIES
+ if (unlikely(req->cookie_ts))
+ TCP_SKB_CB(skb)->when = cookie_init_timestamp(req);
+ else
+#endif
TCP_SKB_CB(skb)->when = tcp_time_stamp;
tcp_syn_build_options((__be32 *)(th + 1), dst_metric(dst, RTAX_ADVMSS), ireq->tstamp_ok,
ireq->sack_ok, ireq->wscale_ok, ireq->rcv_wscale,
diff --git a/net/ipv6/syncookies.c b/net/ipv6/syncookies.c
index 3a622e7abc0..938ce4ecde5 100644
--- a/net/ipv6/syncookies.c
+++ b/net/ipv6/syncookies.c
@@ -170,6 +170,7 @@ 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;
@@ -182,6 +183,13 @@ struct sock *cookie_v6_check(struct sock *sk, struct sk_buff *skb)
NET_INC_STATS_BH(LINUX_MIB_SYNCOOKIESRECV);
+ /* check for timestamp cookie support */
+ memset(&tcp_opt, 0, sizeof(tcp_opt));
+ tcp_parse_options(skb, &tcp_opt, 0);
+
+ if (tcp_opt.saw_tstamp)
+ cookie_check_timestamp(&tcp_opt);
+
ret = NULL;
req = inet6_reqsk_alloc(&tcp6_request_sock_ops);
if (!req)
@@ -216,8 +224,12 @@ struct sock *cookie_v6_check(struct sock *sk, struct sk_buff *skb)
req->expires = 0UL;
req->retrans = 0;
- ireq->snd_wscale = ireq->rcv_wscale = ireq->tstamp_ok = 0;
- ireq->wscale_ok = ireq->sack_ok = 0;
+ ireq->snd_wscale = tcp_opt.snd_wscale;
+ ireq->rcv_wscale = tcp_opt.rcv_wscale;
+ ireq->sack_ok = tcp_opt.sack_ok;
+ ireq->wscale_ok = tcp_opt.wscale_ok;
+ ireq->tstamp_ok = tcp_opt.saw_tstamp;
+ req->ts_recent = tcp_opt.saw_tstamp ? tcp_opt.rcv_tsval : 0;
treq->rcv_isn = ntohl(th->seq) - 1;
treq->snt_isn = cookie;
@@ -253,10 +265,10 @@ struct sock *cookie_v6_check(struct sock *sk, struct sk_buff *skb)
goto out;
}
- req->window_clamp = dst_metric(dst, RTAX_WINDOW);
+ req->window_clamp = tp->window_clamp ? :dst_metric(dst, RTAX_WINDOW);
tcp_select_initial_window(tcp_full_space(sk), req->mss,
&req->rcv_wnd, &req->window_clamp,
- 0, &rcv_wscale);
+ ireq->wscale_ok, &rcv_wscale);
ireq->rcv_wscale = rcv_wscale;
diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index 378cc4002a7..8ebf6de2956 100644
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -1290,10 +1290,8 @@ static int tcp_v6_conn_request(struct sock *sk, struct sk_buff *skb)
tcp_parse_options(skb, &tmp_opt, 0);
- if (want_cookie) {
+ if (want_cookie && !tmp_opt.saw_tstamp)
tcp_clear_options(&tmp_opt);
- tmp_opt.saw_tstamp = 0;
- }
tmp_opt.tstamp_ok = tmp_opt.saw_tstamp;
tcp_openreq_init(req, &tmp_opt, skb);
@@ -1307,6 +1305,7 @@ static int tcp_v6_conn_request(struct sock *sk, struct sk_buff *skb)
if (want_cookie) {
isn = cookie_v6_init_sequence(sk, skb, &req->mss);
+ req->cookie_ts = tmp_opt.tstamp_ok;
} else if (!isn) {
if (ipv6_opt_accepted(sk, skb) ||
np->rxopt.bits.rxinfo || np->rxopt.bits.rxoinfo ||
generated by cgit v1.2.3 (git 2.25.1) at 2024-07-07 18:00:07 +0000