[PATCH net-next 00/17] dccp/tcp: constify listener sock

[PATCH net-next 00/17] dccp/tcp: constify listener sock

[Eric Dumazet]

Another patch bomb to prepare lockless TCP/DCCP LISTEN handling. 

SYNACK retransmits are built and sent without listener socket
being locked. Soon, initial SYNACK packets will have same property.

This series makes sure we did not something wrong with this model,
by adding a const qualifier in all the paths taken from synack building
and transmit, for IPv4/IPv6 and TCP/dccp.

The only potential problem was the rewrite of ecn bits for connections
with DCTCP as congestion module, but this was a very minor one.

Eric Dumazet (17):
  tcp: constify listener socket in tcp_v[46]_init_req()
  tcp: constify tcp_openreq_init_rwin()
  inet: constify ip_route_output_flow() socket argument
  inet: constify inet_csk_route_req() socket argument
  ipv6: constify ip6_dst_lookup_{flow|tail}() sock arguments
  ipv6: constify inet6_csk_route_req() socket argument
  inet: constify ip_dont_fragment() arguments
  tcp: md5: constify tcp_md5_do_lookup() socket argument
  ip: constify ip_build_and_send_pkt() socket argument
  tcp: remove tcp_synack_options() socket argument
  tcp: remove tcp_ecn_make_synack() socket argument
  tcp: constify tcp_make_synack() socket argument
  ipv6: constify ip6_xmit() sock argument
  tcp: constify tcp_v{4|6}_send_synack() socket argument
  dccp: constify dccp_make_response() socket argument
  tcp/dccp: constify rtx_synack() and friends
  inet: constify inet_rtx_syn_ack() sock argument
---
David, to apply these patches you'll need to merge net tree into net-next
first. Thanks !

 include/net/dst.h                   |  9 ++++---
 include/net/inet6_connection_sock.h |  2 +-
 include/net/inet_connection_sock.h  |  2 +-
 include/net/ip.h                    | 10 +++++---
 include/net/ipv6.h                  |  4 +--
 include/net/request_sock.h          |  4 +--
 include/net/route.h                 |  2 +-
 include/net/tcp.h                   | 22 ++++++++--------
 net/dccp/dccp.h                     |  2 +-
 net/dccp/ipv4.c                     |  2 +-
 net/dccp/ipv6.c                     |  2 +-
 net/dccp/output.c                   | 17 ++++++++-----
 net/ipv4/inet_connection_sock.c     |  4 +--
 net/ipv4/ip_output.c                | 14 +++++-----
 net/ipv4/route.c                    |  2 +-
 net/ipv4/tcp_cong.c                 | 12 +++++++--
 net/ipv4/tcp_ipv4.c                 | 11 ++++----
 net/ipv4/tcp_minisocks.c            | 28 ++++++++++++--------
 net/ipv4/tcp_output.c               | 51 +++++++++++++++++++------------------
 net/ipv6/datagram.c                 |  2 +-
 net/ipv6/inet6_connection_sock.c    |  2 +-
 net/ipv6/ip6_output.c               | 30 +++++++++++++++-------
 net/ipv6/tcp_ipv6.c                 | 15 ++++++-----
 net/xfrm/xfrm_policy.c              |  6 ++---
 24 files changed, 149 insertions(+), 106 deletions(-)

-- 
2.6.0.rc2.230.g3dd15c0

[PATCH net-next 01/17] tcp: constify listener socket in tcp_v[46]_init_req()

[Eric Dumazet]

Soon, listener socket spinlock will no longer be held,
add const arguments to tcp_v[46]_init_req() to make clear these
functions can not mess socket fields.

Signed-off-by: Eric Dumazet <edumazet@google.com>
---
 include/net/tcp.h   | 3 ++-
 net/ipv4/tcp_ipv4.c | 3 ++-
 net/ipv6/tcp_ipv6.c | 9 +++++----
 3 files changed, 9 insertions(+), 6 deletions(-)

diff --git a/include/net/tcp.h b/include/net/tcp.h
index 8397d49b47d4..50af10ef1a3d 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -1705,7 +1705,8 @@ struct tcp_request_sock_ops {
 					  const struct sock *sk,
 					  const struct sk_buff *skb);
 #endif
-	void (*init_req)(struct request_sock *req, struct sock *sk,
+	void (*init_req)(struct request_sock *req,
+			 const struct sock *sk_listener,
 			 struct sk_buff *skb);
 #ifdef CONFIG_SYN_COOKIES
 	__u32 (*cookie_init_seq)(struct sock *sk, const struct sk_buff *skb,
diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index 7e2646542312..9d968ca7b669 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -1168,7 +1168,8 @@ static bool tcp_v4_inbound_md5_hash(struct sock *sk,
 }
 #endif
 
-static void tcp_v4_init_req(struct request_sock *req, struct sock *sk_listener,
+static void tcp_v4_init_req(struct request_sock *req,
+			    const struct sock *sk_listener,
 			    struct sk_buff *skb)
 {
 	struct inet_request_sock *ireq = inet_rsk(req);
diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index a004e0b0b3e9..9016797445a2 100644
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -663,22 +663,23 @@ static bool tcp_v6_inbound_md5_hash(struct sock *sk, const struct sk_buff *skb)
 }
 #endif
 
-static void tcp_v6_init_req(struct request_sock *req, struct sock *sk,
+static void tcp_v6_init_req(struct request_sock *req,
+			    const struct sock *sk_listener,
 			    struct sk_buff *skb)
 {
 	struct inet_request_sock *ireq = inet_rsk(req);
-	struct ipv6_pinfo *np = inet6_sk(sk);
+	const struct ipv6_pinfo *np = inet6_sk(sk_listener);
 
 	ireq->ir_v6_rmt_addr = ipv6_hdr(skb)->saddr;
 	ireq->ir_v6_loc_addr = ipv6_hdr(skb)->daddr;
 
 	/* So that link locals have meaning */
-	if (!sk->sk_bound_dev_if &&
+	if (!sk_listener->sk_bound_dev_if &&
 	    ipv6_addr_type(&ireq->ir_v6_rmt_addr) & IPV6_ADDR_LINKLOCAL)
 		ireq->ir_iif = tcp_v6_iif(skb);
 
 	if (!TCP_SKB_CB(skb)->tcp_tw_isn &&
-	    (ipv6_opt_accepted(sk, skb, &TCP_SKB_CB(skb)->header.h6) ||
+	    (ipv6_opt_accepted(sk_listener, skb, &TCP_SKB_CB(skb)->header.h6) ||
 	     np->rxopt.bits.rxinfo ||
 	     np->rxopt.bits.rxoinfo || np->rxopt.bits.rxhlim ||
 	     np->rxopt.bits.rxohlim || np->repflow)) {
-- 
2.6.0.rc2.230.g3dd15c0

[PATCH net-next 02/17] tcp: constify tcp_openreq_init_rwin()

[Eric Dumazet]

Soon, listener socket wont be locked when tcp_openreq_init_rwin()
is called. We need to read socket fields once, as their value
could change under us.

Signed-off-by: Eric Dumazet <edumazet@google.com>
---
 include/net/tcp.h        |  3 ++-
 net/ipv4/tcp_minisocks.c | 28 ++++++++++++++++++----------
 2 files changed, 20 insertions(+), 11 deletions(-)

diff --git a/include/net/tcp.h b/include/net/tcp.h
index 50af10ef1a3d..a89ec41fa3d9 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -1207,7 +1207,8 @@ static inline int tcp_full_space(const struct sock *sk)
 }
 
 extern void tcp_openreq_init_rwin(struct request_sock *req,
-				  struct sock *sk, struct dst_entry *dst);
+				  const struct sock *sk_listener,
+				  const struct dst_entry *dst);
 
 void tcp_enter_memory_pressure(struct sock *sk);
 
diff --git a/net/ipv4/tcp_minisocks.c b/net/ipv4/tcp_minisocks.c
index 6e23c36d26e9..e4fe62b6b106 100644
--- a/net/ipv4/tcp_minisocks.c
+++ b/net/ipv4/tcp_minisocks.c
@@ -361,27 +361,35 @@ void tcp_twsk_destructor(struct sock *sk)
 }
 EXPORT_SYMBOL_GPL(tcp_twsk_destructor);
 
+/* Warning : This function is called without sk_listener being locked.
+ * Be sure to read socket fields once, as their value could change under us.
+ */
 void tcp_openreq_init_rwin(struct request_sock *req,
-			   struct sock *sk, struct dst_entry *dst)
+			   const struct sock *sk_listener,
+			   const struct dst_entry *dst)
 {
 	struct inet_request_sock *ireq = inet_rsk(req);
-	struct tcp_sock *tp = tcp_sk(sk);
-	__u8 rcv_wscale;
+	const struct tcp_sock *tp = tcp_sk(sk_listener);
+	u16 user_mss = READ_ONCE(tp->rx_opt.user_mss);
+	int full_space = tcp_full_space(sk_listener);
 	int mss = dst_metric_advmss(dst);
+	u32 window_clamp;
+	__u8 rcv_wscale;
 
-	if (tp->rx_opt.user_mss && tp->rx_opt.user_mss < mss)
-		mss = tp->rx_opt.user_mss;
+	if (user_mss && user_mss < mss)
+		mss = user_mss;
 
+	window_clamp = READ_ONCE(tp->window_clamp);
 	/* Set this up on the first call only */
-	req->window_clamp = tp->window_clamp ? : dst_metric(dst, RTAX_WINDOW);
+	req->window_clamp = window_clamp ? : dst_metric(dst, RTAX_WINDOW);
 
 	/* limit the window selection if the user enforce a smaller rx buffer */
-	if (sk->sk_userlocks & SOCK_RCVBUF_LOCK &&
-	    (req->window_clamp > tcp_full_space(sk) || req->window_clamp == 0))
-		req->window_clamp = tcp_full_space(sk);
+	if (sk_listener->sk_userlocks & SOCK_RCVBUF_LOCK &&
+	    (req->window_clamp > full_space || req->window_clamp == 0))
+		req->window_clamp = full_space;
 
 	/* tcp_full_space because it is guaranteed to be the first packet */
-	tcp_select_initial_window(tcp_full_space(sk),
+	tcp_select_initial_window(full_space,
 		mss - (ireq->tstamp_ok ? TCPOLEN_TSTAMP_ALIGNED : 0),
 		&req->rcv_wnd,
 		&req->window_clamp,
-- 
2.6.0.rc2.230.g3dd15c0

[PATCH net-next 03/17] inet: constify ip_route_output_flow() socket argument

[Eric Dumazet]

Very soon, TCP stack might call inet_csk_route_req(), which
calls inet_csk_route_req() with an unlocked listener socket,
so we need to make sure ip_route_output_flow() is not trying to
change any field from its socket argument.

Signed-off-by: Eric Dumazet <edumazet@google.com>
---
 include/net/dst.h      | 9 +++++----
 include/net/route.h    | 2 +-
 net/ipv4/route.c       | 2 +-
 net/xfrm/xfrm_policy.c | 6 +++---
 4 files changed, 10 insertions(+), 9 deletions(-)

diff --git a/include/net/dst.h b/include/net/dst.h
index df0481a07029..779206c15f8b 100644
--- a/include/net/dst.h
+++ b/include/net/dst.h
@@ -489,7 +489,8 @@ struct flowi;
 #ifndef CONFIG_XFRM
 static inline struct dst_entry *xfrm_lookup(struct net *net,
 					    struct dst_entry *dst_orig,
-					    const struct flowi *fl, struct sock *sk,
+					    const struct flowi *fl,
+					    const struct sock *sk,
 					    int flags)
 {
 	return dst_orig;
@@ -498,7 +499,7 @@ static inline struct dst_entry *xfrm_lookup(struct net *net,
 static inline struct dst_entry *xfrm_lookup_route(struct net *net,
 						  struct dst_entry *dst_orig,
 						  const struct flowi *fl,
-						  struct sock *sk,
+						  const struct sock *sk,
 						  int flags)
 {
 	return dst_orig;
@@ -511,11 +512,11 @@ static inline struct xfrm_state *dst_xfrm(const struct dst_entry *dst)
 
 #else
 struct dst_entry *xfrm_lookup(struct net *net, struct dst_entry *dst_orig,
-			      const struct flowi *fl, struct sock *sk,
+			      const struct flowi *fl, const struct sock *sk,
 			      int flags);
 
 struct dst_entry *xfrm_lookup_route(struct net *net, struct dst_entry *dst_orig,
-				    const struct flowi *fl, struct sock *sk,
+				    const struct flowi *fl, const struct sock *sk,
 				    int flags);
 
 /* skb attached with this dst needs transformation if dst->xfrm is valid */
diff --git a/include/net/route.h b/include/net/route.h
index 10a7d21a211c..414beadc619f 100644
--- a/include/net/route.h
+++ b/include/net/route.h
@@ -114,7 +114,7 @@ void rt_cache_flush(struct net *net);
 void rt_flush_dev(struct net_device *dev);
 struct rtable *__ip_route_output_key(struct net *, struct flowi4 *flp);
 struct rtable *ip_route_output_flow(struct net *, struct flowi4 *flp,
-				    struct sock *sk);
+				    const struct sock *sk);
 struct dst_entry *ipv4_blackhole_route(struct net *net,
 				       struct dst_entry *dst_orig);
 
diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index 80f7c5b7b832..f7afcba8b1a1 100644
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -2291,7 +2291,7 @@ struct dst_entry *ipv4_blackhole_route(struct net *net, struct dst_entry *dst_or
 }
 
 struct rtable *ip_route_output_flow(struct net *net, struct flowi4 *flp4,
-				    struct sock *sk)
+				    const struct sock *sk)
 {
 	struct rtable *rt = __ip_route_output_key(net, flp4);
 
diff --git a/net/xfrm/xfrm_policy.c b/net/xfrm/xfrm_policy.c
index e7f64bcb78a8..418daa038edf 100644
--- a/net/xfrm/xfrm_policy.c
+++ b/net/xfrm/xfrm_policy.c
@@ -1208,7 +1208,7 @@ static inline int policy_to_flow_dir(int dir)
 	}
 }
 
-static struct xfrm_policy *xfrm_sk_policy_lookup(struct sock *sk, int dir,
+static struct xfrm_policy *xfrm_sk_policy_lookup(const struct sock *sk, int dir,
 						 const struct flowi *fl)
 {
 	struct xfrm_policy *pol;
@@ -2185,7 +2185,7 @@ static struct dst_entry *make_blackhole(struct net *net, u16 family,
  */
 struct dst_entry *xfrm_lookup(struct net *net, struct dst_entry *dst_orig,
 			      const struct flowi *fl,
-			      struct sock *sk, int flags)
+			      const struct sock *sk, int flags)
 {
 	struct xfrm_policy *pols[XFRM_POLICY_TYPE_MAX];
 	struct flow_cache_object *flo;
@@ -2333,7 +2333,7 @@ EXPORT_SYMBOL(xfrm_lookup);
  */
 struct dst_entry *xfrm_lookup_route(struct net *net, struct dst_entry *dst_orig,
 				    const struct flowi *fl,
-				    struct sock *sk, int flags)
+				    const struct sock *sk, int flags)
 {
 	struct dst_entry *dst = xfrm_lookup(net, dst_orig, fl, sk,
 					    flags | XFRM_LOOKUP_QUEUE |
-- 
2.6.0.rc2.230.g3dd15c0

[PATCH net-next 04/17] inet: constify inet_csk_route_req() socket argument

[Eric Dumazet]

This is used by TCP listener core, and listener socket shall
not be modified by inet_csk_route_req().

Signed-off-by: Eric Dumazet <edumazet@google.com>
---
 include/net/inet_connection_sock.h | 2 +-
 net/ipv4/inet_connection_sock.c    | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/include/net/inet_connection_sock.h b/include/net/inet_connection_sock.h
index 0320bbb7d7b5..00c3ced6ee55 100644
--- a/include/net/inet_connection_sock.h
+++ b/include/net/inet_connection_sock.h
@@ -266,7 +266,7 @@ int inet_csk_bind_conflict(const struct sock *sk,
 			   const struct inet_bind_bucket *tb, bool relax);
 int inet_csk_get_port(struct sock *sk, unsigned short snum);
 
-struct dst_entry *inet_csk_route_req(struct sock *sk, struct flowi4 *fl4,
+struct dst_entry *inet_csk_route_req(const struct sock *sk, struct flowi4 *fl4,
 				     const struct request_sock *req);
 struct dst_entry *inet_csk_route_child_sock(struct sock *sk, struct sock *newsk,
 					    const struct request_sock *req);
diff --git a/net/ipv4/inet_connection_sock.c b/net/ipv4/inet_connection_sock.c
index 7bb9c39e0a4d..631301406f7e 100644
--- a/net/ipv4/inet_connection_sock.c
+++ b/net/ipv4/inet_connection_sock.c
@@ -408,7 +408,7 @@ void inet_csk_reset_keepalive_timer(struct sock *sk, unsigned long len)
 }
 EXPORT_SYMBOL(inet_csk_reset_keepalive_timer);
 
-struct dst_entry *inet_csk_route_req(struct sock *sk,
+struct dst_entry *inet_csk_route_req(const struct sock *sk,
 				     struct flowi4 *fl4,
 				     const struct request_sock *req)
 {
-- 
2.6.0.rc2.230.g3dd15c0

[PATCH net-next 05/17] ipv6: constify ip6_dst_lookup_{flow|tail}() sock arguments

[Eric Dumazet]

ip6_dst_lookup_flow() and ip6_dst_lookup_tail() do not touch
socket, lets add a const qualifier.

This will permit the same change in inet6_csk_route_req()

Signed-off-by: Eric Dumazet <edumazet@google.com>
---
 include/net/ipv6.h    | 2 +-
 net/ipv6/ip6_output.c | 4 ++--
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/include/net/ipv6.h b/include/net/ipv6.h
index 384a93cf07d6..9877b68ad207 100644
--- a/include/net/ipv6.h
+++ b/include/net/ipv6.h
@@ -849,7 +849,7 @@ static inline struct sk_buff *ip6_finish_skb(struct sock *sk)
 
 int ip6_dst_lookup(struct net *net, struct sock *sk, struct dst_entry **dst,
 		   struct flowi6 *fl6);
-struct dst_entry *ip6_dst_lookup_flow(struct sock *sk, struct flowi6 *fl6,
+struct dst_entry *ip6_dst_lookup_flow(const struct sock *sk, struct flowi6 *fl6,
 				      const struct in6_addr *final_dst);
 struct dst_entry *ip6_sk_dst_lookup_flow(struct sock *sk, struct flowi6 *fl6,
 					 const struct in6_addr *final_dst);
diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c
index 291a07be5dfb..6b0d86f3fbfc 100644
--- a/net/ipv6/ip6_output.c
+++ b/net/ipv6/ip6_output.c
@@ -883,7 +883,7 @@ out:
 	return dst;
 }
 
-static int ip6_dst_lookup_tail(struct net *net, struct sock *sk,
+static int ip6_dst_lookup_tail(struct net *net, const struct sock *sk,
 			       struct dst_entry **dst, struct flowi6 *fl6)
 {
 #ifdef CONFIG_IPV6_OPTIMISTIC_DAD
@@ -1014,7 +1014,7 @@ EXPORT_SYMBOL_GPL(ip6_dst_lookup);
  *	It returns a valid dst pointer on success, or a pointer encoded
  *	error code.
  */
-struct dst_entry *ip6_dst_lookup_flow(struct sock *sk, struct flowi6 *fl6,
+struct dst_entry *ip6_dst_lookup_flow(const struct sock *sk, struct flowi6 *fl6,
 				      const struct in6_addr *final_dst)
 {
 	struct dst_entry *dst = NULL;
-- 
2.6.0.rc2.230.g3dd15c0

[PATCH net-next 06/17] ipv6: constify inet6_csk_route_req() socket argument

[Eric Dumazet]

socket is not modified, make it const so that callers can
do the same if they need.

Signed-off-by: Eric Dumazet <edumazet@google.com>
---
 include/net/inet6_connection_sock.h | 2 +-
 net/ipv6/inet6_connection_sock.c    | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/include/net/inet6_connection_sock.h b/include/net/inet6_connection_sock.h
index 6d539e4e5ba7..81d937e820c4 100644
--- a/include/net/inet6_connection_sock.h
+++ b/include/net/inet6_connection_sock.h
@@ -25,7 +25,7 @@ struct sockaddr;
 int inet6_csk_bind_conflict(const struct sock *sk,
 			    const struct inet_bind_bucket *tb, bool relax);
 
-struct dst_entry *inet6_csk_route_req(struct sock *sk, struct flowi6 *fl6,
+struct dst_entry *inet6_csk_route_req(const struct sock *sk, struct flowi6 *fl6,
 				      const struct request_sock *req);
 
 struct request_sock *inet6_csk_search_req(struct sock *sk,
diff --git a/net/ipv6/inet6_connection_sock.c b/net/ipv6/inet6_connection_sock.c
index 6927f3fb5597..91b7d33f508b 100644
--- a/net/ipv6/inet6_connection_sock.c
+++ b/net/ipv6/inet6_connection_sock.c
@@ -65,7 +65,7 @@ int inet6_csk_bind_conflict(const struct sock *sk,
 }
 EXPORT_SYMBOL_GPL(inet6_csk_bind_conflict);
 
-struct dst_entry *inet6_csk_route_req(struct sock *sk,
+struct dst_entry *inet6_csk_route_req(const struct sock *sk,
 				      struct flowi6 *fl6,
 				      const struct request_sock *req)
 {
-- 
2.6.0.rc2.230.g3dd15c0

[PATCH net-next 07/17] inet: constify ip_dont_fragment() arguments

[Eric Dumazet]

ip_dont_fragment() can accept const socket and dst

Signed-off-by: Eric Dumazet <edumazet@google.com>
---
 include/net/ip.h | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/include/net/ip.h b/include/net/ip.h
index 9b9ca2839399..525dc0778926 100644
--- a/include/net/ip.h
+++ b/include/net/ip.h
@@ -282,10 +282,12 @@ int ip_decrease_ttl(struct iphdr *iph)
 }
 
 static inline
-int ip_dont_fragment(struct sock *sk, struct dst_entry *dst)
+int ip_dont_fragment(const struct sock *sk, const struct dst_entry *dst)
 {
-	return  inet_sk(sk)->pmtudisc == IP_PMTUDISC_DO ||
-		(inet_sk(sk)->pmtudisc == IP_PMTUDISC_WANT &&
+	u8 pmtudisc = READ_ONCE(inet_sk(sk)->pmtudisc);
+
+	return  pmtudisc == IP_PMTUDISC_DO ||
+		(pmtudisc == IP_PMTUDISC_WANT &&
 		 !(dst_metric_locked(dst, RTAX_MTU)));
 }
 
-- 
2.6.0.rc2.230.g3dd15c0

[PATCH net-next 08/17] tcp: md5: constify tcp_md5_do_lookup() socket argument

[Eric Dumazet]

When TCP new listener is done, these functions will be called
without socket lock being held. Make sure they don't change
anything.

Signed-off-by: Eric Dumazet <edumazet@google.com>
---
 include/net/tcp.h   | 10 +++++-----
 net/ipv4/tcp_ipv4.c |  6 +++---
 net/ipv6/tcp_ipv6.c |  4 ++--
 3 files changed, 10 insertions(+), 10 deletions(-)

diff --git a/include/net/tcp.h b/include/net/tcp.h
index a89ec41fa3d9..70aea203545e 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -1372,16 +1372,16 @@ int tcp_md5_do_add(struct sock *sk, const union tcp_md5_addr *addr,
 		   int family, const u8 *newkey, u8 newkeylen, gfp_t gfp);
 int tcp_md5_do_del(struct sock *sk, const union tcp_md5_addr *addr,
 		   int family);
-struct tcp_md5sig_key *tcp_v4_md5_lookup(struct sock *sk,
+struct tcp_md5sig_key *tcp_v4_md5_lookup(const struct sock *sk,
 					 const struct sock *addr_sk);
 
 #ifdef CONFIG_TCP_MD5SIG
-struct tcp_md5sig_key *tcp_md5_do_lookup(struct sock *sk,
+struct tcp_md5sig_key *tcp_md5_do_lookup(const struct sock *sk,
 					 const union tcp_md5_addr *addr,
 					 int family);
 #define tcp_twsk_md5_key(twsk)	((twsk)->tw_md5_key)
 #else
-static inline struct tcp_md5sig_key *tcp_md5_do_lookup(struct sock *sk,
+static inline struct tcp_md5sig_key *tcp_md5_do_lookup(const struct sock *sk,
 					 const union tcp_md5_addr *addr,
 					 int family)
 {
@@ -1684,7 +1684,7 @@ int tcp_conn_request(struct request_sock_ops *rsk_ops,
 /* TCP af-specific functions */
 struct tcp_sock_af_ops {
 #ifdef CONFIG_TCP_MD5SIG
-	struct tcp_md5sig_key	*(*md5_lookup) (struct sock *sk,
+	struct tcp_md5sig_key	*(*md5_lookup) (const struct sock *sk,
 						const struct sock *addr_sk);
 	int		(*calc_md5_hash)(char *location,
 					 const struct tcp_md5sig_key *md5,
@@ -1699,7 +1699,7 @@ struct tcp_sock_af_ops {
 struct tcp_request_sock_ops {
 	u16 mss_clamp;
 #ifdef CONFIG_TCP_MD5SIG
-	struct tcp_md5sig_key *(*req_md5_lookup)(struct sock *sk,
+	struct tcp_md5sig_key *(*req_md5_lookup)(const struct sock *sk,
 						 const struct sock *addr_sk);
 	int		(*calc_md5_hash) (char *location,
 					  const struct tcp_md5sig_key *md5,
diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index 9d968ca7b669..1c1009d783f5 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -865,7 +865,7 @@ static void tcp_v4_reqsk_destructor(struct request_sock *req)
  */
 
 /* Find the Key structure for an address.  */
-struct tcp_md5sig_key *tcp_md5_do_lookup(struct sock *sk,
+struct tcp_md5sig_key *tcp_md5_do_lookup(const struct sock *sk,
 					 const union tcp_md5_addr *addr,
 					 int family)
 {
@@ -877,7 +877,7 @@ struct tcp_md5sig_key *tcp_md5_do_lookup(struct sock *sk,
 	/* caller either holds rcu_read_lock() or socket lock */
 	md5sig = rcu_dereference_check(tp->md5sig_info,
 				       sock_owned_by_user(sk) ||
-				       lockdep_is_held(&sk->sk_lock.slock));
+				       lockdep_is_held((spinlock_t *)&sk->sk_lock.slock));
 	if (!md5sig)
 		return NULL;
 #if IS_ENABLED(CONFIG_IPV6)
@@ -894,7 +894,7 @@ struct tcp_md5sig_key *tcp_md5_do_lookup(struct sock *sk,
 }
 EXPORT_SYMBOL(tcp_md5_do_lookup);
 
-struct tcp_md5sig_key *tcp_v4_md5_lookup(struct sock *sk,
+struct tcp_md5sig_key *tcp_v4_md5_lookup(const struct sock *sk,
 					 const struct sock *addr_sk)
 {
 	const union tcp_md5_addr *addr;
diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index 9016797445a2..1071131a6c53 100644
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -476,13 +476,13 @@ static void tcp_v6_reqsk_destructor(struct request_sock *req)
 }
 
 #ifdef CONFIG_TCP_MD5SIG
-static struct tcp_md5sig_key *tcp_v6_md5_do_lookup(struct sock *sk,
+static struct tcp_md5sig_key *tcp_v6_md5_do_lookup(const struct sock *sk,
 						   const struct in6_addr *addr)
 {
 	return tcp_md5_do_lookup(sk, (union tcp_md5_addr *)addr, AF_INET6);
 }
 
-static struct tcp_md5sig_key *tcp_v6_md5_lookup(struct sock *sk,
+static struct tcp_md5sig_key *tcp_v6_md5_lookup(const struct sock *sk,
 						const struct sock *addr_sk)
 {
 	return tcp_v6_md5_do_lookup(sk, &addr_sk->sk_v6_daddr);
-- 
2.6.0.rc2.230.g3dd15c0

[PATCH net-next 09/17] ip: constify ip_build_and_send_pkt() socket argument

[Eric Dumazet]

This function is used to build and send SYNACK packets,
possibly on behalf of unlocked listener socket.

Make sure we did not miss a write by making this socket const.

We no longer can use ip_select_ident() and have to either
set iph->id to 0 or directly call __ip_select_ident()

Signed-off-by: Eric Dumazet <edumazet@google.com>
---
 include/net/ip.h     |  2 +-
 net/ipv4/ip_output.c | 14 ++++++++------
 2 files changed, 9 insertions(+), 7 deletions(-)

diff --git a/include/net/ip.h b/include/net/ip.h
index 525dc0778926..91a6b2c88341 100644
--- a/include/net/ip.h
+++ b/include/net/ip.h
@@ -100,7 +100,7 @@ int igmp_mc_init(void);
  *	Functions provided by ip.c
  */
 
-int ip_build_and_send_pkt(struct sk_buff *skb, struct sock *sk,
+int ip_build_and_send_pkt(struct sk_buff *skb, const struct sock *sk,
 			  __be32 saddr, __be32 daddr,
 			  struct ip_options_rcu *opt);
 int ip_rcv(struct sk_buff *skb, struct net_device *dev, struct packet_type *pt,
diff --git a/net/ipv4/ip_output.c b/net/ipv4/ip_output.c
index 09a6b7bb7ea3..06d2c87ed505 100644
--- a/net/ipv4/ip_output.c
+++ b/net/ipv4/ip_output.c
@@ -137,7 +137,7 @@ static inline int ip_select_ttl(struct inet_sock *inet, struct dst_entry *dst)
  *		Add an ip header to a skbuff and send it out.
  *
  */
-int ip_build_and_send_pkt(struct sk_buff *skb, struct sock *sk,
+int ip_build_and_send_pkt(struct sk_buff *skb, const struct sock *sk,
 			  __be32 saddr, __be32 daddr, struct ip_options_rcu *opt)
 {
 	struct inet_sock *inet = inet_sk(sk);
@@ -151,15 +151,17 @@ int ip_build_and_send_pkt(struct sk_buff *skb, struct sock *sk,
 	iph->version  = 4;
 	iph->ihl      = 5;
 	iph->tos      = inet->tos;
-	if (ip_dont_fragment(sk, &rt->dst))
-		iph->frag_off = htons(IP_DF);
-	else
-		iph->frag_off = 0;
 	iph->ttl      = ip_select_ttl(inet, &rt->dst);
 	iph->daddr    = (opt && opt->opt.srr ? opt->opt.faddr : daddr);
 	iph->saddr    = saddr;
 	iph->protocol = sk->sk_protocol;
-	ip_select_ident(sock_net(sk), skb, sk);
+	if (ip_dont_fragment(sk, &rt->dst)) {
+		iph->frag_off = htons(IP_DF);
+		iph->id = 0;
+	} else {
+		iph->frag_off = 0;
+		__ip_select_ident(sock_net(sk), iph, 1);
+	}
 
 	if (opt && opt->opt.optlen) {
 		iph->ihl += opt->opt.optlen>>2;
-- 
2.6.0.rc2.230.g3dd15c0

[PATCH net-next 10/17] tcp: remove tcp_synack_options() socket argument

[Eric Dumazet]

We do not use the socket in this function.

Signed-off-by: Eric Dumazet <edumazet@google.com>
---
 net/ipv4/tcp_output.c | 15 +++++++--------
 1 file changed, 7 insertions(+), 8 deletions(-)

diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 1767fe652cb5..ab03018fb621 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -612,12 +612,11 @@ static unsigned int tcp_syn_options(struct sock *sk, struct sk_buff *skb,
 }
 
 /* Set up TCP options for SYN-ACKs. */
-static unsigned int tcp_synack_options(struct sock *sk,
-				   struct request_sock *req,
-				   unsigned int mss, struct sk_buff *skb,
-				   struct tcp_out_options *opts,
-				   const struct tcp_md5sig_key *md5,
-				   struct tcp_fastopen_cookie *foc)
+static unsigned int tcp_synack_options(struct request_sock *req,
+				       unsigned int mss, struct sk_buff *skb,
+				       struct tcp_out_options *opts,
+				       const struct tcp_md5sig_key *md5,
+				       struct tcp_fastopen_cookie *foc)
 {
 	struct inet_request_sock *ireq = inet_rsk(req);
 	unsigned int remaining = MAX_TCP_OPTION_SPACE;
@@ -2990,8 +2989,8 @@ struct sk_buff *tcp_make_synack(struct sock *sk, struct dst_entry *dst,
 	md5 = tcp_rsk(req)->af_specific->req_md5_lookup(sk, req_to_sk(req));
 #endif
 	skb_set_hash(skb, tcp_rsk(req)->txhash, PKT_HASH_TYPE_L4);
-	tcp_header_size = tcp_synack_options(sk, req, mss, skb, &opts, md5,
-					     foc) + sizeof(*th);
+	tcp_header_size = tcp_synack_options(req, mss, skb, &opts, md5, foc) +
+			  sizeof(*th);
 
 	skb_push(skb, tcp_header_size);
 	skb_reset_transport_header(skb);
-- 
2.6.0.rc2.230.g3dd15c0

[PATCH net-next 11/17] tcp: remove tcp_ecn_make_synack() socket argument

[Eric Dumazet]

SYNACK packets might be sent without holding socket lock.

For DCTCP/ECN sake, we should call INET_ECN_xmit() while
socket lock is owned, and only when we init/change congestion control.

This also fixies a bug if congestion module is changed from
dctcp to another one on a listener : we now clear ECN bits
properly.

Signed-off-by: Eric Dumazet <edumazet@google.com>
---
 net/ipv4/tcp_cong.c   | 12 ++++++++++--
 net/ipv4/tcp_output.c | 10 +++-------
 2 files changed, 13 insertions(+), 9 deletions(-)

diff --git a/net/ipv4/tcp_cong.c b/net/ipv4/tcp_cong.c
index 93c4dc3ab23f..882caa4e72bc 100644
--- a/net/ipv4/tcp_cong.c
+++ b/net/ipv4/tcp_cong.c
@@ -173,6 +173,10 @@ out:
 	 */
 	if (ca->get_info)
 		memset(icsk->icsk_ca_priv, 0, sizeof(icsk->icsk_ca_priv));
+	if (ca->flags & TCP_CONG_NEEDS_ECN)
+		INET_ECN_xmit(sk);
+	else
+		INET_ECN_dontxmit(sk);
 }
 
 void tcp_init_congestion_control(struct sock *sk)
@@ -181,6 +185,10 @@ void tcp_init_congestion_control(struct sock *sk)
 
 	if (icsk->icsk_ca_ops->init)
 		icsk->icsk_ca_ops->init(sk);
+	if (tcp_ca_needs_ecn(sk))
+		INET_ECN_xmit(sk);
+	else
+		INET_ECN_dontxmit(sk);
 }
 
 static void tcp_reinit_congestion_control(struct sock *sk,
@@ -192,8 +200,8 @@ static void tcp_reinit_congestion_control(struct sock *sk,
 	icsk->icsk_ca_ops = ca;
 	icsk->icsk_ca_setsockopt = 1;
 
-	if (sk->sk_state != TCP_CLOSE && icsk->icsk_ca_ops->init)
-		icsk->icsk_ca_ops->init(sk);
+	if (sk->sk_state != TCP_CLOSE)
+		tcp_init_congestion_control(sk);
 }
 
 /* Manage refcounts on socket close. */
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index ab03018fb621..dcb5c144f8fa 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -357,14 +357,10 @@ static void tcp_ecn_clear_syn(struct sock *sk, struct sk_buff *skb)
 }
 
 static void
-tcp_ecn_make_synack(const struct request_sock *req, struct tcphdr *th,
-		    struct sock *sk)
+tcp_ecn_make_synack(const struct request_sock *req, struct tcphdr *th)
 {
-	if (inet_rsk(req)->ecn_ok) {
+	if (inet_rsk(req)->ecn_ok)
 		th->ece = 1;
-		if (tcp_ca_needs_ecn(sk))
-			INET_ECN_xmit(sk);
-	}
 }
 
 /* Set up ECN state for a packet on a ESTABLISHED socket that is about to
@@ -2999,7 +2995,7 @@ struct sk_buff *tcp_make_synack(struct sock *sk, struct dst_entry *dst,
 	memset(th, 0, sizeof(struct tcphdr));
 	th->syn = 1;
 	th->ack = 1;
-	tcp_ecn_make_synack(req, th, sk);
+	tcp_ecn_make_synack(req, th);
 	th->source = htons(ireq->ir_num);
 	th->dest = ireq->ir_rmt_port;
 	/* Setting of flags are superfluous here for callers (and ECE is
-- 
2.6.0.rc2.230.g3dd15c0

[PATCH net-next 12/17] tcp: constify tcp_make_synack() socket argument

[Eric Dumazet]

listener socket is not locked when tcp_make_synack() is called.

We better make sure no field is written.

There is one exception : Since SYNACK packets are attached to the listener
at this moment (or SYN_RECV child in case of Fast Open),
sock_wmalloc() needs to update sk->sk_wmem_alloc, but this is done using
atomic operations so this is safe.

Signed-off-by: Eric Dumazet <edumazet@google.com>
---
 include/net/tcp.h     |  2 +-
 net/ipv4/tcp_output.c | 24 +++++++++++++++---------
 2 files changed, 16 insertions(+), 10 deletions(-)

diff --git a/include/net/tcp.h b/include/net/tcp.h
index 70aea203545e..fde20acb3328 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -461,7 +461,7 @@ struct sock *tcp_v4_syn_recv_sock(struct sock *sk, struct sk_buff *skb,
 int tcp_v4_do_rcv(struct sock *sk, struct sk_buff *skb);
 int tcp_v4_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len);
 int tcp_connect(struct sock *sk);
-struct sk_buff *tcp_make_synack(struct sock *sk, struct dst_entry *dst,
+struct sk_buff *tcp_make_synack(const struct sock *sk, struct dst_entry *dst,
 				struct request_sock *req,
 				struct tcp_fastopen_cookie *foc);
 int tcp_disconnect(struct sock *sk, int flags);
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index dcb5c144f8fa..0831dcae6d03 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -2945,20 +2945,25 @@ int tcp_send_synack(struct sock *sk)
  * Allocate one skb and build a SYNACK packet.
  * @dst is consumed : Caller should not use it again.
  */
-struct sk_buff *tcp_make_synack(struct sock *sk, struct dst_entry *dst,
+struct sk_buff *tcp_make_synack(const struct sock *sk, struct dst_entry *dst,
 				struct request_sock *req,
 				struct tcp_fastopen_cookie *foc)
 {
-	struct tcp_out_options opts;
 	struct inet_request_sock *ireq = inet_rsk(req);
-	struct tcp_sock *tp = tcp_sk(sk);
-	struct tcphdr *th;
-	struct sk_buff *skb;
+	const struct tcp_sock *tp = tcp_sk(sk);
 	struct tcp_md5sig_key *md5 = NULL;
+	struct tcp_out_options opts;
+	struct sk_buff *skb;
 	int tcp_header_size;
+	struct tcphdr *th;
+	u16 user_mss;
 	int mss;
 
-	skb = sock_wmalloc(sk, MAX_TCP_HEADER, 1, GFP_ATOMIC);
+	/* sk is a const pointer, because we want to express multiple cpus
+	 * might call us concurrently.
+	 * sock_wmalloc() will change sk->sk_wmem_alloc in an atomic way.
+	 */
+	skb = sock_wmalloc((struct sock *)sk, MAX_TCP_HEADER, 1, GFP_ATOMIC);
 	if (unlikely(!skb)) {
 		dst_release(dst);
 		return NULL;
@@ -2969,8 +2974,9 @@ struct sk_buff *tcp_make_synack(struct sock *sk, struct dst_entry *dst,
 	skb_dst_set(skb, dst);
 
 	mss = dst_metric_advmss(dst);
-	if (tp->rx_opt.user_mss && tp->rx_opt.user_mss < mss)
-		mss = tp->rx_opt.user_mss;
+	user_mss = READ_ONCE(tp->rx_opt.user_mss);
+	if (user_mss && user_mss < mss)
+		mss = user_mss;
 
 	memset(&opts, 0, sizeof(opts));
 #ifdef CONFIG_SYN_COOKIES
@@ -3010,7 +3016,7 @@ 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));
-	tcp_options_write((__be32 *)(th + 1), tp, &opts);
+	tcp_options_write((__be32 *)(th + 1), NULL, &opts);
 	th->doff = (tcp_header_size >> 2);
 	TCP_INC_STATS_BH(sock_net(sk), TCP_MIB_OUTSEGS);
 
-- 
2.6.0.rc2.230.g3dd15c0

[PATCH net-next 13/17] ipv6: constify ip6_xmit() sock argument

[Eric Dumazet]

This is to document that socket lock might not be held at this point.

skb_set_owner_w() and ipv6_local_error() are using proper atomic ops
or spinlocks, so we promote the socket to non const when calling them.

netfilter hooks should never assume socket lock is held,
we also promote the socket to non const.

Signed-off-by: Eric Dumazet <edumazet@google.com>
---
 include/net/ipv6.h    |  2 +-
 net/ipv6/datagram.c   |  2 +-
 net/ipv6/ip6_output.c | 26 +++++++++++++++++++-------
 3 files changed, 21 insertions(+), 9 deletions(-)

diff --git a/include/net/ipv6.h b/include/net/ipv6.h
index 9877b68ad207..3dde042bcd3f 100644
--- a/include/net/ipv6.h
+++ b/include/net/ipv6.h
@@ -812,7 +812,7 @@ int ip6_rcv_finish(struct net *net, struct sock *sk, struct sk_buff *skb);
 /*
  *	upper-layer output functions
  */
-int ip6_xmit(struct sock *sk, struct sk_buff *skb, struct flowi6 *fl6,
+int ip6_xmit(const struct sock *sk, struct sk_buff *skb, struct flowi6 *fl6,
 	     struct ipv6_txoptions *opt, int tclass);
 
 int ip6_find_1stfragopt(struct sk_buff *skb, u8 **nexthdr);
diff --git a/net/ipv6/datagram.c b/net/ipv6/datagram.c
index 9aadd57808a5..d70b0238f468 100644
--- a/net/ipv6/datagram.c
+++ b/net/ipv6/datagram.c
@@ -263,7 +263,7 @@ void ipv6_icmp_error(struct sock *sk, struct sk_buff *skb, int err,
 
 void ipv6_local_error(struct sock *sk, int err, struct flowi6 *fl6, u32 info)
 {
-	struct ipv6_pinfo *np = inet6_sk(sk);
+	const struct ipv6_pinfo *np = inet6_sk(sk);
 	struct sock_exterr_skb *serr;
 	struct ipv6hdr *iph;
 	struct sk_buff *skb;
diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c
index 6b0d86f3fbfc..60c565309d0a 100644
--- a/net/ipv6/ip6_output.c
+++ b/net/ipv6/ip6_output.c
@@ -150,14 +150,16 @@ int ip6_output(struct sock *sk, struct sk_buff *skb)
 }
 
 /*
- *	xmit an sk_buff (used by TCP, SCTP and DCCP)
+ * xmit an sk_buff (used by TCP, SCTP and DCCP)
+ * Note : socket lock is not held for SYNACK packets, but might be modified
+ * by calls to skb_set_owner_w() and ipv6_local_error(),
+ * which are using proper atomic operations or spinlocks.
  */
-
-int ip6_xmit(struct sock *sk, struct sk_buff *skb, struct flowi6 *fl6,
+int ip6_xmit(const struct sock *sk, struct sk_buff *skb, struct flowi6 *fl6,
 	     struct ipv6_txoptions *opt, int tclass)
 {
 	struct net *net = sock_net(sk);
-	struct ipv6_pinfo *np = inet6_sk(sk);
+	const struct ipv6_pinfo *np = inet6_sk(sk);
 	struct in6_addr *first_hop = &fl6->daddr;
 	struct dst_entry *dst = skb_dst(skb);
 	struct ipv6hdr *hdr;
@@ -186,7 +188,10 @@ int ip6_xmit(struct sock *sk, struct sk_buff *skb, struct flowi6 *fl6,
 			}
 			consume_skb(skb);
 			skb = skb2;
-			skb_set_owner_w(skb, sk);
+			/* skb_set_owner_w() changes sk->sk_wmem_alloc atomically,
+			 * it is safe to call in our context (socket lock not held)
+			 */
+			skb_set_owner_w(skb, (struct sock *)sk);
 		}
 		if (opt->opt_flen)
 			ipv6_push_frag_opts(skb, opt, &proto);
@@ -224,13 +229,20 @@ int ip6_xmit(struct sock *sk, struct sk_buff *skb, struct flowi6 *fl6,
 	if ((skb->len <= mtu) || skb->ignore_df || skb_is_gso(skb)) {
 		IP6_UPD_PO_STATS(net, ip6_dst_idev(skb_dst(skb)),
 			      IPSTATS_MIB_OUT, skb->len);
+		/* hooks should never assume socket lock is held.
+		 * we promote our socket to non const
+		 */
 		return NF_HOOK(NFPROTO_IPV6, NF_INET_LOCAL_OUT,
-			       net, sk, skb, NULL, dst->dev,
+			       net, (struct sock *)sk, skb, NULL, dst->dev,
 			       dst_output_okfn);
 	}
 
 	skb->dev = dst->dev;
-	ipv6_local_error(sk, EMSGSIZE, fl6, mtu);
+	/* ipv6_local_error() does not require socket lock,
+	 * we promote our socket to non const
+	 */
+	ipv6_local_error((struct sock *)sk, EMSGSIZE, fl6, mtu);
+
 	IP6_INC_STATS(net, ip6_dst_idev(skb_dst(skb)), IPSTATS_MIB_FRAGFAILS);
 	kfree_skb(skb);
 	return -EMSGSIZE;
-- 
2.6.0.rc2.230.g3dd15c0

[PATCH net-next 14/17] tcp: constify tcp_v{4|6}_send_synack() socket argument

[Eric Dumazet]

This documents fact that listener lock might not be held
at the time SYNACK are sent.

Signed-off-by: Eric Dumazet <edumazet@google.com>
---
 include/net/tcp.h   | 2 +-
 net/ipv4/tcp_ipv4.c | 2 +-
 net/ipv6/tcp_ipv6.c | 2 +-
 3 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/include/net/tcp.h b/include/net/tcp.h
index fde20acb3328..0f847eb9af65 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -1717,7 +1717,7 @@ struct tcp_request_sock_ops {
 				       const struct request_sock *req,
 				       bool *strict);
 	__u32 (*init_seq)(const struct sk_buff *skb);
-	int (*send_synack)(struct sock *sk, struct dst_entry *dst,
+	int (*send_synack)(const struct sock *sk, struct dst_entry *dst,
 			   struct flowi *fl, struct request_sock *req,
 			   u16 queue_mapping, struct tcp_fastopen_cookie *foc);
 	void (*queue_hash_add)(struct sock *sk, struct request_sock *req,
diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index 1c1009d783f5..a23ba7daecbf 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -818,7 +818,7 @@ static void tcp_v4_reqsk_send_ack(struct sock *sk, struct sk_buff *skb,
  *	This still operates on a request_sock only, not on a big
  *	socket.
  */
-static int tcp_v4_send_synack(struct sock *sk, struct dst_entry *dst,
+static int tcp_v4_send_synack(const struct sock *sk, struct dst_entry *dst,
 			      struct flowi *fl,
 			      struct request_sock *req,
 			      u16 queue_mapping,
diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index 1071131a6c53..16fb299dcab8 100644
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -434,7 +434,7 @@ out:
 }
 
 
-static int tcp_v6_send_synack(struct sock *sk, struct dst_entry *dst,
+static int tcp_v6_send_synack(const struct sock *sk, struct dst_entry *dst,
 			      struct flowi *fl,
 			      struct request_sock *req,
 			      u16 queue_mapping,
-- 
2.6.0.rc2.230.g3dd15c0

[PATCH net-next 15/17] dccp: constify dccp_make_response() socket argument

[Eric Dumazet]

Like tcp_make_synack() the only time we might change the socket is
when calling sock_wmalloc(), which is using atomic operation to
update sk->sk_wmem_alloc

Also use MAX_DCCP_HEADER as both IPv4/IPv6 use this value for max_header.

Signed-off-by: Eric Dumazet <edumazet@google.com>
---
 net/dccp/dccp.h   |  2 +-
 net/dccp/output.c | 17 +++++++++++------
 2 files changed, 12 insertions(+), 7 deletions(-)

diff --git a/net/dccp/dccp.h b/net/dccp/dccp.h
index bebc735f5afc..31e96df500d1 100644
--- a/net/dccp/dccp.h
+++ b/net/dccp/dccp.h
@@ -293,7 +293,7 @@ int dccp_init_sock(struct sock *sk, const __u8 ctl_sock_initialized);
 void dccp_destroy_sock(struct sock *sk);
 
 void dccp_close(struct sock *sk, long timeout);
-struct sk_buff *dccp_make_response(struct sock *sk, struct dst_entry *dst,
+struct sk_buff *dccp_make_response(const struct sock *sk, struct dst_entry *dst,
 				   struct request_sock *req);
 
 int dccp_connect(struct sock *sk);
diff --git a/net/dccp/output.c b/net/dccp/output.c
index 0248e8a3460c..4ce912e691d0 100644
--- a/net/dccp/output.c
+++ b/net/dccp/output.c
@@ -390,7 +390,7 @@ int dccp_retransmit_skb(struct sock *sk)
 	return dccp_transmit_skb(sk, skb_clone(sk->sk_send_head, GFP_ATOMIC));
 }
 
-struct sk_buff *dccp_make_response(struct sock *sk, struct dst_entry *dst,
+struct sk_buff *dccp_make_response(const struct sock *sk, struct dst_entry *dst,
 				   struct request_sock *req)
 {
 	struct dccp_hdr *dh;
@@ -398,13 +398,18 @@ struct sk_buff *dccp_make_response(struct sock *sk, struct dst_entry *dst,
 	const u32 dccp_header_size = sizeof(struct dccp_hdr) +
 				     sizeof(struct dccp_hdr_ext) +
 				     sizeof(struct dccp_hdr_response);
-	struct sk_buff *skb = sock_wmalloc(sk, sk->sk_prot->max_header, 1,
-					   GFP_ATOMIC);
-	if (skb == NULL)
+	struct sk_buff *skb;
+
+	/* sk is marked const to clearly express we dont hold socket lock.
+	 * sock_wmalloc() will atomically change sk->sk_wmem_alloc,
+	 * it is safe to promote sk to non const.
+	 */
+	skb = sock_wmalloc((struct sock *)sk, MAX_DCCP_HEADER, 1,
+			   GFP_ATOMIC);
+	if (!skb)
 		return NULL;
 
-	/* Reserve space for headers. */
-	skb_reserve(skb, sk->sk_prot->max_header);
+	skb_reserve(skb, MAX_DCCP_HEADER);
 
 	skb_dst_set(skb, dst_clone(dst));
 
-- 
2.6.0.rc2.230.g3dd15c0

[PATCH net-next 16/17] tcp/dccp: constify rtx_synack() and friends

[Eric Dumazet]

This is done to make sure we do not change listener socket
while sending SYNACK packets while socket lock is not held.

Signed-off-by: Eric Dumazet <edumazet@google.com>
---
 include/net/request_sock.h | 2 +-
 include/net/tcp.h          | 2 +-
 net/dccp/ipv4.c            | 2 +-
 net/dccp/ipv6.c            | 2 +-
 net/ipv4/tcp_output.c      | 2 +-
 5 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/include/net/request_sock.h b/include/net/request_sock.h
index 87935cad2f7b..ff7ce1e53ed4 100644
--- a/include/net/request_sock.h
+++ b/include/net/request_sock.h
@@ -32,7 +32,7 @@ struct request_sock_ops {
 	int		obj_size;
 	struct kmem_cache	*slab;
 	char		*slab_name;
-	int		(*rtx_syn_ack)(struct sock *sk,
+	int		(*rtx_syn_ack)(const struct sock *sk,
 				       struct request_sock *req);
 	void		(*send_ack)(struct sock *sk, struct sk_buff *skb,
 				    struct request_sock *req);
diff --git a/include/net/tcp.h b/include/net/tcp.h
index 0f847eb9af65..cdbf63d3c5cf 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -1676,7 +1676,7 @@ int tcp4_proc_init(void);
 void tcp4_proc_exit(void);
 #endif
 
-int tcp_rtx_synack(struct sock *sk, struct request_sock *req);
+int tcp_rtx_synack(const struct sock *sk, struct request_sock *req);
 int tcp_conn_request(struct request_sock_ops *rsk_ops,
 		     const struct tcp_request_sock_ops *af_ops,
 		     struct sock *sk, struct sk_buff *skb);
diff --git a/net/dccp/ipv4.c b/net/dccp/ipv4.c
index ccf4c5629b3c..a46ae9c69ccf 100644
--- a/net/dccp/ipv4.c
+++ b/net/dccp/ipv4.c
@@ -498,7 +498,7 @@ static struct dst_entry* dccp_v4_route_skb(struct net *net, struct sock *sk,
 	return &rt->dst;
 }
 
-static int dccp_v4_send_response(struct sock *sk, struct request_sock *req)
+static int dccp_v4_send_response(const struct sock *sk, struct request_sock *req)
 {
 	int err = -1;
 	struct sk_buff *skb;
diff --git a/net/dccp/ipv6.c b/net/dccp/ipv6.c
index 5165571f397a..4fa199dc69a3 100644
--- a/net/dccp/ipv6.c
+++ b/net/dccp/ipv6.c
@@ -181,7 +181,7 @@ out:
 }
 
 
-static int dccp_v6_send_response(struct sock *sk, struct request_sock *req)
+static int dccp_v6_send_response(const struct sock *sk, struct request_sock *req)
 {
 	struct inet_request_sock *ireq = inet_rsk(req);
 	struct ipv6_pinfo *np = inet6_sk(sk);
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 0831dcae6d03..9e53dd9bfcad 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -3503,7 +3503,7 @@ void tcp_send_probe0(struct sock *sk)
 				  TCP_RTO_MAX);
 }
 
-int tcp_rtx_synack(struct sock *sk, struct request_sock *req)
+int tcp_rtx_synack(const struct sock *sk, struct request_sock *req)
 {
 	const struct tcp_request_sock_ops *af_ops = tcp_rsk(req)->af_specific;
 	struct flowi fl;
-- 
2.6.0.rc2.230.g3dd15c0

[PATCH net-next 17/17] inet: constify inet_rtx_syn_ack() sock argument

[Eric Dumazet]

SYNACK packets are sent on behalf on unlocked listeners
or fastopen sockets. Mark socket as const to catch future changes
that might break the assumption.

Signed-off-by: Eric Dumazet <edumazet@google.com>
---
 include/net/request_sock.h      | 2 +-
 net/ipv4/inet_connection_sock.c | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/include/net/request_sock.h b/include/net/request_sock.h
index ff7ce1e53ed4..181f97f9fe1c 100644
--- a/include/net/request_sock.h
+++ b/include/net/request_sock.h
@@ -42,7 +42,7 @@ struct request_sock_ops {
 	void		(*syn_ack_timeout)(const struct request_sock *req);
 };
 
-int inet_rtx_syn_ack(struct sock *parent, struct request_sock *req);
+int inet_rtx_syn_ack(const struct sock *parent, struct request_sock *req);
 
 /* struct request_sock - mini sock to represent a connection request
  */
diff --git a/net/ipv4/inet_connection_sock.c b/net/ipv4/inet_connection_sock.c
index 631301406f7e..ba2f90d90cb5 100644
--- a/net/ipv4/inet_connection_sock.c
+++ b/net/ipv4/inet_connection_sock.c
@@ -563,7 +563,7 @@ static inline void syn_ack_recalc(struct request_sock *req, const int thresh,
 		  req->num_timeout >= rskq_defer_accept - 1;
 }
 
-int inet_rtx_syn_ack(struct sock *parent, struct request_sock *req)
+int inet_rtx_syn_ack(const struct sock *parent, struct request_sock *req)
 {
 	int err = req->rsk_ops->rtx_syn_ack(parent, req);
 
-- 
2.6.0.rc2.230.g3dd15c0

Re: [PATCH net-next 00/17] dccp/tcp: constify listener sock

[David Miller]

From: Eric Dumazet <edumazet@google.com>
Date: Fri, 25 Sep 2015 07:39:07 -0700

> Another patch bomb to prepare lockless TCP/DCCP LISTEN handling. 
> 
> SYNACK retransmits are built and sent without listener socket
> being locked. Soon, initial SYNACK packets will have same property.
> 
> This series makes sure we did not something wrong with this model,
> by adding a const qualifier in all the paths taken from synack building
> and transmit, for IPv4/IPv6 and TCP/dccp.
> 
> The only potential problem was the rewrite of ecn bits for connections
> with DCTCP as congestion module, but this was a very minor one.
 ...
> David, to apply these patches you'll need to merge net tree into net-next
> first. Thanks !

I was able to apply them cleanly to net-next as-is, so I did so.

Re: [PATCH net-next 00/17] dccp/tcp: constify listener sock

[Eric Dumazet]

On Fri, 2015-09-25 at 13:42 -0700, David Miller wrote:
> From: Eric Dumazet <edumazet@google.com>
> Date: Fri, 25 Sep 2015 07:39:07 -0700
> 
> > Another patch bomb to prepare lockless TCP/DCCP LISTEN handling. 
> > 
> > SYNACK retransmits are built and sent without listener socket
> > being locked. Soon, initial SYNACK packets will have same property.
> > 
> > This series makes sure we did not something wrong with this model,
> > by adding a const qualifier in all the paths taken from synack building
> > and transmit, for IPv4/IPv6 and TCP/dccp.
> > 
> > The only potential problem was the rewrite of ecn bits for connections
> > with DCTCP as congestion module, but this was a very minor one.
>  ...
> > David, to apply these patches you'll need to merge net tree into net-next
> > first. Thanks !
> 
> I was able to apply them cleanly to net-next as-is, so I did so.

Ah, perfect then ;)

Thanks !