Skip to content

Commit

Permalink
tcp: Factorise cookie-dependent fields initialisation in cookie_v[46]…
Browse files Browse the repository at this point in the history 
…_check()

We will support arbitrary SYN Cookie with BPF, and then kfunc at
TC will preallocate reqsk and initialise some fields that should
not be overwritten later by cookie_v[46]_check().

To simplify the flow in cookie_v[46]_check(), we move such fields'
initialisation to cookie_tcp_reqsk_alloc() and factorise non-BPF
SYN Cookie handling into cookie_tcp_check(), where we validate the
cookie and allocate reqsk, as done by kfunc later.

Note that we set ireq->ecn_ok in two steps, the latter of which will
be shared by the BPF case.  As cookie_ecn_ok() is one-liner, now
it's inlined.

Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Link: https://lore.kernel.org/r/20231129022924.96156-9-kuniyu@amazon.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
  • Loading branch information
Kuniyuki Iwashima authored and Jakub Kicinski committed Nov 30, 2023
1 parent de5626b commit 8e7bab6
Show file tree
Hide file tree
Showing 3 changed files with 99 additions and 81 deletions.
13 changes: 10 additions & 3 deletions include/net/tcp.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -494,7 +494,10 @@ struct sock *tcp_get_cookie_sock(struct sock *sk, struct sk_buff *skb,
int __cookie_v4_check(const struct iphdr *iph, const struct tcphdr *th);
struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb);
struct request_sock *cookie_tcp_reqsk_alloc(const struct request_sock_ops *ops,
struct sock *sk, struct sk_buff *skb);
struct sock *sk, struct sk_buff *skb,
struct tcp_options_received *tcp_opt,
int mss, u32 tsoff);

#ifdef CONFIG_SYN_COOKIES

/* Syncookies use a monotonic timer which increments every 60 seconds.
Expand Down Expand Up @@ -580,8 +583,12 @@ __u32 cookie_v4_init_sequence(const struct sk_buff *skb, __u16 *mss);
u64 cookie_init_timestamp(struct request_sock *req, u64 now);
bool cookie_timestamp_decode(const struct net *net,
struct tcp_options_received *opt);
bool cookie_ecn_ok(const struct tcp_options_received *opt,
const struct net *net, const struct dst_entry *dst);

static inline bool cookie_ecn_ok(const struct net *net, const struct dst_entry *dst)
{
return READ_ONCE(net->ipv4.sysctl_tcp_ecn) ||
dst_feature(dst, RTAX_FEATURE_ECN);
}

/* From net/ipv6/syncookies.c */
int __cookie_v6_check(const struct ipv6hdr *iph, const struct tcphdr *th);
Expand Down
106 changes: 57 additions & 49 deletions net/ipv4/syncookies.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -270,21 +270,6 @@ bool cookie_timestamp_decode(const struct net *net,
}
EXPORT_SYMBOL(cookie_timestamp_decode);

bool cookie_ecn_ok(const struct tcp_options_received *tcp_opt,
const struct net *net, const struct dst_entry *dst)
{
bool ecn_ok = tcp_opt->rcv_tsecr & TS_OPT_ECN;

if (!ecn_ok)
return false;

if (READ_ONCE(net->ipv4.sysctl_tcp_ecn))
return true;

return dst_feature(dst, RTAX_FEATURE_ECN);
}
EXPORT_SYMBOL(cookie_ecn_ok);

static int cookie_tcp_reqsk_init(struct sock *sk, struct sk_buff *skb,
struct request_sock *req)
{
Expand Down Expand Up @@ -320,8 +305,12 @@ static int cookie_tcp_reqsk_init(struct sock *sk, struct sk_buff *skb,
}

struct request_sock *cookie_tcp_reqsk_alloc(const struct request_sock_ops *ops,
struct sock *sk, struct sk_buff *skb)
struct sock *sk, struct sk_buff *skb,
struct tcp_options_received *tcp_opt,
int mss, u32 tsoff)
{
struct inet_request_sock *ireq;
struct tcp_request_sock *treq;
struct request_sock *req;

if (sk_is_mptcp(sk))
Expand All @@ -337,40 +326,36 @@ struct request_sock *cookie_tcp_reqsk_alloc(const struct request_sock_ops *ops,
return NULL;
}

ireq = inet_rsk(req);
treq = tcp_rsk(req);

req->mss = mss;
req->ts_recent = tcp_opt->saw_tstamp ? tcp_opt->rcv_tsval : 0;

ireq->snd_wscale = tcp_opt->snd_wscale;
ireq->tstamp_ok = tcp_opt->saw_tstamp;
ireq->sack_ok = tcp_opt->sack_ok;
ireq->wscale_ok = tcp_opt->wscale_ok;
ireq->ecn_ok = !!(tcp_opt->rcv_tsecr & TS_OPT_ECN);

treq->ts_off = tsoff;

return req;
}
EXPORT_SYMBOL_GPL(cookie_tcp_reqsk_alloc);

/* On input, sk is a listener.
* Output is listener if incoming packet would not create a child
* NULL if memory could not be allocated.
*/
struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb)
static struct request_sock *cookie_tcp_check(struct net *net, struct sock *sk,
struct sk_buff *skb)
{
struct ip_options *opt = &TCP_SKB_CB(skb)->header.h4.opt;
const struct tcphdr *th = tcp_hdr(skb);
struct tcp_options_received tcp_opt;
struct tcp_sock *tp = tcp_sk(sk);
struct inet_request_sock *ireq;
struct net *net = sock_net(sk);
struct tcp_request_sock *treq;
struct request_sock *req;
struct sock *ret = sk;
int full_space, mss;
struct flowi4 fl4;
struct rtable *rt;
__u8 rcv_wscale;
u32 tsoff = 0;

if (!READ_ONCE(net->ipv4.sysctl_tcp_syncookies) ||
!th->ack || th->rst)
goto out;
int mss;

if (tcp_synq_no_recent_overflow(sk))
goto out;

mss = __cookie_v4_check(ip_hdr(skb), th);
if (mss == 0) {
mss = __cookie_v4_check(ip_hdr(skb), tcp_hdr(skb));
if (!mss) {
__NET_INC_STATS(net, LINUX_MIB_SYNCOOKIESFAILED);
goto out;
}
Expand All @@ -391,21 +376,44 @@ struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb)
if (!cookie_timestamp_decode(net, &tcp_opt))
goto out;

req = cookie_tcp_reqsk_alloc(&tcp_request_sock_ops, sk, skb);
return cookie_tcp_reqsk_alloc(&tcp_request_sock_ops, sk, skb,
&tcp_opt, mss, tsoff);
out:
return ERR_PTR(-EINVAL);
}

/* On input, sk is a listener.
* Output is listener if incoming packet would not create a child
* NULL if memory could not be allocated.
*/
struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb)
{
struct ip_options *opt = &TCP_SKB_CB(skb)->header.h4.opt;
const struct tcphdr *th = tcp_hdr(skb);
struct tcp_sock *tp = tcp_sk(sk);
struct inet_request_sock *ireq;
struct net *net = sock_net(sk);
struct request_sock *req;
struct sock *ret = sk;
struct flowi4 fl4;
struct rtable *rt;
__u8 rcv_wscale;
int full_space;

if (!READ_ONCE(net->ipv4.sysctl_tcp_syncookies) ||
!th->ack || th->rst)
goto out;

req = cookie_tcp_check(net, sk, skb);
if (IS_ERR(req))
goto out;
if (!req)
goto out_drop;

ireq = inet_rsk(req);
treq = tcp_rsk(req);
treq->ts_off = tsoff;
req->mss = mss;

sk_rcv_saddr_set(req_to_sk(req), ip_hdr(skb)->daddr);
sk_daddr_set(req_to_sk(req), ip_hdr(skb)->saddr);
ireq->snd_wscale = tcp_opt.snd_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)
Expand Down Expand Up @@ -447,7 +455,7 @@ struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb)
dst_metric(&rt->dst, RTAX_INITRWND));

ireq->rcv_wscale = rcv_wscale;
ireq->ecn_ok = cookie_ecn_ok(&tcp_opt, net, &rt->dst);
ireq->ecn_ok &= cookie_ecn_ok(net, &rt->dst);

ret = tcp_get_cookie_sock(sk, skb, req, &rt->dst);
/* ip_queue_xmit() depends on our flow being setup
Expand Down
61 changes: 32 additions & 29 deletions net/ipv6/syncookies.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -127,31 +127,18 @@ int __cookie_v6_check(const struct ipv6hdr *iph, const struct tcphdr *th)
}
EXPORT_SYMBOL_GPL(__cookie_v6_check);

struct sock *cookie_v6_check(struct sock *sk, struct sk_buff *skb)
static struct request_sock *cookie_tcp_check(struct net *net, struct sock *sk,
struct sk_buff *skb)
{
const struct tcphdr *th = tcp_hdr(skb);
struct ipv6_pinfo *np = inet6_sk(sk);
struct tcp_options_received tcp_opt;
struct tcp_sock *tp = tcp_sk(sk);
struct inet_request_sock *ireq;
struct net *net = sock_net(sk);
struct tcp_request_sock *treq;
struct request_sock *req;
struct dst_entry *dst;
struct sock *ret = sk;
int full_space, mss;
__u8 rcv_wscale;
u32 tsoff = 0;

if (!READ_ONCE(net->ipv4.sysctl_tcp_syncookies) ||
!th->ack || th->rst)
goto out;
int mss;

if (tcp_synq_no_recent_overflow(sk))
goto out;

mss = __cookie_v6_check(ipv6_hdr(skb), th);
if (mss == 0) {
mss = __cookie_v6_check(ipv6_hdr(skb), tcp_hdr(skb));
if (!mss) {
__NET_INC_STATS(net, LINUX_MIB_SYNCOOKIESFAILED);
goto out;
}
Expand All @@ -172,14 +159,37 @@ struct sock *cookie_v6_check(struct sock *sk, struct sk_buff *skb)
if (!cookie_timestamp_decode(net, &tcp_opt))
goto out;

req = cookie_tcp_reqsk_alloc(&tcp6_request_sock_ops, sk, skb);
return cookie_tcp_reqsk_alloc(&tcp6_request_sock_ops, sk, skb,
&tcp_opt, mss, tsoff);
out:
return ERR_PTR(-EINVAL);
}

struct sock *cookie_v6_check(struct sock *sk, struct sk_buff *skb)
{
const struct tcphdr *th = tcp_hdr(skb);
struct ipv6_pinfo *np = inet6_sk(sk);
struct tcp_sock *tp = tcp_sk(sk);
struct inet_request_sock *ireq;
struct net *net = sock_net(sk);
struct request_sock *req;
struct dst_entry *dst;
struct sock *ret = sk;
__u8 rcv_wscale;
int full_space;

if (!READ_ONCE(net->ipv4.sysctl_tcp_syncookies) ||
!th->ack || th->rst)
goto out;

req = cookie_tcp_check(net, sk, skb);
if (IS_ERR(req))
goto out;
if (!req)
goto out_drop;

ireq = inet_rsk(req);
treq = tcp_rsk(req);

req->mss = mss;
ireq->ir_v6_rmt_addr = ipv6_hdr(skb)->saddr;
ireq->ir_v6_loc_addr = ipv6_hdr(skb)->daddr;

Expand All @@ -198,13 +208,6 @@ struct sock *cookie_v6_check(struct sock *sk, struct sk_buff *skb)
ipv6_addr_type(&ireq->ir_v6_rmt_addr) & IPV6_ADDR_LINKLOCAL)
ireq->ir_iif = tcp_v6_iif(skb);

ireq->snd_wscale = tcp_opt.snd_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->ts_off = tsoff;

tcp_ao_syncookie(sk, skb, req, AF_INET6);

/*
Expand Down Expand Up @@ -245,7 +248,7 @@ struct sock *cookie_v6_check(struct sock *sk, struct sk_buff *skb)
dst_metric(dst, RTAX_INITRWND));

ireq->rcv_wscale = rcv_wscale;
ireq->ecn_ok = cookie_ecn_ok(&tcp_opt, net, dst);
ireq->ecn_ok &= cookie_ecn_ok(net, dst);

ret = tcp_get_cookie_sock(sk, skb, req, dst);
out:
Expand Down

0 comments on commit 8e7bab6

Please sign in to comment.