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Date: Fri, 5 May 2017 02:32:08 +0200
From: Florian Westphal <fw@...len.de>
To: Florian Westphal <fw@...len.de>
Cc: Eric Dumazet <eric.dumazet@...il.com>,
David Miller <davem@...emloft.net>,
netdev <netdev@...r.kernel.org>,
Yuchung Cheng <ycheng@...gle.com>
Subject: Re: [PATCH net] tcp: randomize timestamps on syncookies
Florian Westphal <fw@...len.de> wrote:
[..]
> This breaks syncookies w. timestamps; cookie_timestamp_decode() lacks a tsoff
> for readjustment.
>
> We also need to pass the (recomputed) tsoff to tcp_get_cookie_sock().
This small delta makes things work for me:
diff --git a/include/net/tcp.h b/include/net/tcp.h
index 1be353fc5cb1..8c0e5a901d64 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -470,7 +470,7 @@ void inet_sk_rx_dst_set(struct sock *sk, const struct sk_buff *skb);
/* From syncookies.c */
struct sock *tcp_get_cookie_sock(struct sock *sk, struct sk_buff *skb,
struct request_sock *req,
- struct dst_entry *dst);
+ struct dst_entry *dst, u32 tsoff);
int __cookie_v4_check(const struct iphdr *iph, const struct tcphdr *th,
u32 cookie);
struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb);
diff --git a/net/ipv4/syncookies.c b/net/ipv4/syncookies.c
index 496b97e17aaf..39bfdc94bf44 100644
--- a/net/ipv4/syncookies.c
+++ b/net/ipv4/syncookies.c
@@ -16,6 +16,7 @@
#include <linux/siphash.h>
#include <linux/kernel.h>
#include <linux/export.h>
+#include <net/secure_seq.h>
#include <net/tcp.h>
#include <net/route.h>
@@ -203,7 +204,7 @@ EXPORT_SYMBOL_GPL(__cookie_v4_check);
struct sock *tcp_get_cookie_sock(struct sock *sk, struct sk_buff *skb,
struct request_sock *req,
- struct dst_entry *dst)
+ struct dst_entry *dst, u32 tsoff)
{
struct inet_connection_sock *icsk = inet_csk(sk);
struct sock *child;
@@ -213,6 +214,7 @@ struct sock *tcp_get_cookie_sock(struct sock *sk, struct sk_buff *skb,
NULL, &own_req);
if (child) {
atomic_set(&req->rsk_refcnt, 1);
+ tcp_sk(child)->tsoffset = tsoff;
sock_rps_save_rxhash(child, skb);
inet_csk_reqsk_queue_add(sk, req, child);
} else {
@@ -292,6 +294,7 @@ struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb)
struct rtable *rt;
__u8 rcv_wscale;
struct flowi4 fl4;
+ u32 tsoff;
if (!sock_net(sk)->ipv4.sysctl_tcp_syncookies || !th->ack || th->rst)
goto out;
@@ -311,6 +314,12 @@ struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb)
memset(&tcp_opt, 0, sizeof(tcp_opt));
tcp_parse_options(skb, &tcp_opt, 0, NULL);
+ tsoff = 0;
+ if (tcp_opt.saw_tstamp && tcp_opt.rcv_tsecr) {
+ tsoff = secure_tcp_ts_off(ip_hdr(skb)->daddr, ip_hdr(skb)->saddr);
+ tcp_opt.rcv_tsecr -= tsoff;
+ }
+
if (!cookie_timestamp_decode(&tcp_opt))
goto out;
@@ -381,7 +390,7 @@ struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb)
ireq->rcv_wscale = rcv_wscale;
ireq->ecn_ok = cookie_ecn_ok(&tcp_opt, sock_net(sk), &rt->dst);
- ret = tcp_get_cookie_sock(sk, skb, req, &rt->dst);
+ ret = tcp_get_cookie_sock(sk, skb, req, &rt->dst, tsoff);
/* ip_queue_xmit() depends on our flow being setup
* Normal sockets get it right from inet_csk_route_child_sock()
*/
diff --git a/net/ipv6/syncookies.c b/net/ipv6/syncookies.c
index 895ff650db43..eb96825d6340 100644
--- a/net/ipv6/syncookies.c
+++ b/net/ipv6/syncookies.c
@@ -18,6 +18,7 @@
#include <linux/random.h>
#include <linux/siphash.h>
#include <linux/kernel.h>
+#include <net/secure_seq.h>
#include <net/ipv6.h>
#include <net/tcp.h>
@@ -143,6 +144,7 @@ struct sock *cookie_v6_check(struct sock *sk, struct sk_buff *skb)
int mss;
struct dst_entry *dst;
__u8 rcv_wscale;
+ u32 tsoff;
if (!sock_net(sk)->ipv4.sysctl_tcp_syncookies || !th->ack || th->rst)
goto out;
@@ -162,6 +164,12 @@ struct sock *cookie_v6_check(struct sock *sk, struct sk_buff *skb)
memset(&tcp_opt, 0, sizeof(tcp_opt));
tcp_parse_options(skb, &tcp_opt, 0, NULL);
+ tsoff = 0;
+ if (tcp_opt.saw_tstamp && tcp_opt.rcv_tsecr) {
+ tsoff = secure_tcpv6_ts_off(&ip_hdr(skb)->daddr, &ip_hdr(skb)->saddr);
+ tcp_opt.rcv_tsecr -= tsoff;
+ }
+
if (!cookie_timestamp_decode(&tcp_opt))
goto out;
@@ -242,7 +250,7 @@ struct sock *cookie_v6_check(struct sock *sk, struct sk_buff *skb)
ireq->rcv_wscale = rcv_wscale;
ireq->ecn_ok = cookie_ecn_ok(&tcp_opt, sock_net(sk), dst);
- ret = tcp_get_cookie_sock(sk, skb, req, dst);
+ ret = tcp_get_cookie_sock(sk, skb, req, dst, tsoff);
out:
return ret;
out_free:
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