unimore/kernel-hacking-2024-linux-steffo
unimore/kernel-hacking-2024-linux-steffo
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tcp: avoid two atomic ops for syncookies

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inet_reqsk_alloc() is used to allocate a temporary request
in order to generate a SYNACK with a cookie. Then later,
syncookie validation also uses a temporary request.

These paths already took a reference on listener refcount,
we can avoid a couple of atomic operations.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet 2015-10-04 21:08:11 -07:00 committed by David S. Miller
parent 004a5d0140
commit a1a5344ddb
7 changed files with 19 additions and 11 deletions
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3
include/net/inet_sock.h
View file

@ -245,7 +245,8 @@ static inline unsigned int __inet_ehashfn(const __be32 laddr,
} }
struct request_sock *inet_reqsk_alloc(const struct request_sock_ops *ops, struct request_sock *inet_reqsk_alloc(const struct request_sock_ops *ops,
struct sock *sk_listener); struct sock *sk_listener,
bool attach_listener);
static inline __u8 inet_sk_flowi_flags(const struct sock *sk) static inline __u8 inet_sk_flowi_flags(const struct sock *sk)
{ {

11
include/net/request_sock.h
View file

@ -80,7 +80,8 @@ static inline struct sock *req_to_sk(struct request_sock *req)
} }
static inline struct request_sock * static inline struct request_sock *
reqsk_alloc(const struct request_sock_ops *ops, struct sock *sk_listener) reqsk_alloc(const struct request_sock_ops *ops, struct sock *sk_listener,
bool attach_listener)
{ {
struct request_sock *req; struct request_sock *req;
@ -88,8 +89,12 @@ reqsk_alloc(const struct request_sock_ops *ops, struct sock *sk_listener)
if (req) { if (req) {
req->rsk_ops = ops; req->rsk_ops = ops;
sock_hold(sk_listener); if (attach_listener) {
req->rsk_listener = sk_listener; sock_hold(sk_listener);
req->rsk_listener = sk_listener;
} else {
req->rsk_listener = NULL;
}
req_to_sk(req)->sk_prot = sk_listener->sk_prot; req_to_sk(req)->sk_prot = sk_listener->sk_prot;
sk_node_init(&req_to_sk(req)->sk_node); sk_node_init(&req_to_sk(req)->sk_node);
sk_tx_queue_clear(req_to_sk(req)); sk_tx_queue_clear(req_to_sk(req));

2
net/dccp/ipv4.c
View file

@ -595,7 +595,7 @@ int dccp_v4_conn_request(struct sock *sk, struct sk_buff *skb)
if (sk_acceptq_is_full(sk) && inet_csk_reqsk_queue_young(sk) > 1) if (sk_acceptq_is_full(sk) && inet_csk_reqsk_queue_young(sk) > 1)
goto drop; goto drop;
req = inet_reqsk_alloc(&dccp_request_sock_ops, sk); req = inet_reqsk_alloc(&dccp_request_sock_ops, sk, true);
if (req == NULL) if (req == NULL)
goto drop; goto drop;

2
net/dccp/ipv6.c
View file

@ -319,7 +319,7 @@ static int dccp_v6_conn_request(struct sock *sk, struct sk_buff *skb)
if (sk_acceptq_is_full(sk) && inet_csk_reqsk_queue_young(sk) > 1) if (sk_acceptq_is_full(sk) && inet_csk_reqsk_queue_young(sk) > 1)
goto drop; goto drop;
req = inet_reqsk_alloc(&dccp6_request_sock_ops, sk); req = inet_reqsk_alloc(&dccp6_request_sock_ops, sk, true);
if (req == NULL) if (req == NULL)
goto drop; goto drop;

2
net/ipv4/syncookies.c
View file

@ -326,7 +326,7 @@ struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb)
goto out; goto out;
ret = NULL; ret = NULL;
req = inet_reqsk_alloc(&tcp_request_sock_ops, sk); /* for safety */ req = inet_reqsk_alloc(&tcp_request_sock_ops, sk, false); /* for safety */
if (!req) if (!req)
goto out; goto out;

8
net/ipv4/tcp_input.c
View file

@ -6042,9 +6042,11 @@ static void tcp_openreq_init(struct request_sock *req,
} }
struct request_sock *inet_reqsk_alloc(const struct request_sock_ops *ops, struct request_sock *inet_reqsk_alloc(const struct request_sock_ops *ops,
struct sock *sk_listener) struct sock *sk_listener,
bool attach_listener)
{ {
struct request_sock *req = reqsk_alloc(ops, sk_listener); struct request_sock *req = reqsk_alloc(ops, sk_listener,
attach_listener);
if (req) { if (req) {
struct inet_request_sock *ireq = inet_rsk(req); struct inet_request_sock *ireq = inet_rsk(req);
@ -6143,7 +6145,7 @@ int tcp_conn_request(struct request_sock_ops *rsk_ops,
goto drop; goto drop;
} }
req = inet_reqsk_alloc(rsk_ops, sk); req = inet_reqsk_alloc(rsk_ops, sk, !want_cookie);
if (!req) if (!req)
goto drop; goto drop;

2
net/ipv6/syncookies.c
View file

@ -170,7 +170,7 @@ struct sock *cookie_v6_check(struct sock *sk, struct sk_buff *skb)
goto out; goto out;
ret = NULL; ret = NULL;
req = inet_reqsk_alloc(&tcp6_request_sock_ops, sk); req = inet_reqsk_alloc(&tcp6_request_sock_ops, sk, false);
if (!req) if (!req)
goto out; goto out;