diff mbox series

[net-next,2/3] net/smc: Limits backlog connections

Message ID 9b52fc3f11a2ae6f23224a178fd4cff9f9dd4eaa.1643284658.git.alibuda@linux.alibaba.com (mailing list archive)
State Not Applicable
Headers show
Series Optimizing performance in short-lived | expand

Commit Message

D. Wythe Jan. 27, 2022, 12:08 p.m. UTC 
From: "D. Wythe" <alibuda@linux.alibaba.com>

Current implementation does not handling backlog semantics, one
potential risk is that server will be flooded by infinite amount
connections, even if client was SMC-incapable.

This patch works to put a limit on backlog connections, referring to the
TCP implementation, we divides SMC connections into two categories:

1. Half SMC connection, which includes all TCP established while SMC not
connections.

2. Full SMC connection, which includes all SMC established connections.

For half SMC connection, since all half SMC connections starts with TCP
established, we can achieve our goal by put a limit before TCP
established. Refer to the implementation of TCP, this limits will based
on not only the half SMC connections but also the full connections,
which is also a constraint on full SMC connections.

For full SMC connections, although we know exactly where it starts, it's
quite hard to put a limit before it. The easiest way is to block wait
before receive SMC confirm CLC message, while it's under protection by
smc_server_lgr_pending, a global lock, which leads this limit to the
entire host instead of a single listen socket. Another way is to drop
the full connections, but considering the cast of SMC connections, we
prefer to keep full SMC connections.

Even so, the limits of full SMC connections still exists, see commits
about half SMC connection below.

After this patch, the limits of backend connection shows like:

For SMC:

1. Client with SMC-capability can makes 2 * backlog full SMC connections
   or 1 * backlog half SMC connections and 1 * backlog full SMC
   connections at most.

2. Client without SMC-capability can only makes 1 * backlog half TCP
   connections and 1 * backlog full TCP connections.

Signed-off-by: D. Wythe <alibuda@linux.alibaba.com>
---
 net/smc/af_smc.c | 43 +++++++++++++++++++++++++++++++++++++++++++
 net/smc/smc.h    |  4 ++++
 2 files changed, 47 insertions(+)

Comments

kernel test robot Jan. 27, 2022, 3:52 p.m. UTC | #1 
Hi Wythe",

Thank you for the patch! Perhaps something to improve:

[auto build test WARNING on net-next/master]

url:    https://github.com/0day-ci/linux/commits/D-Wythe/Optimizing-performance-in-short-lived/20220127-200912
base:   https://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next.git fbb8295248e1d6f576d444309fcf79356008eac1
config: arc-allyesconfig (https://download.01.org/0day-ci/archive/20220127/202201272349.KA4IX9hr-lkp@intel.com/config)
compiler: arceb-elf-gcc (GCC) 11.2.0
reproduce (this is a W=1 build):
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # https://github.com/0day-ci/linux/commit/718aff24f3fcc73ecb7bff17fcbe029b799c6624
        git remote add linux-review https://github.com/0day-ci/linux
        git fetch --no-tags linux-review D-Wythe/Optimizing-performance-in-short-lived/20220127-200912
        git checkout 718aff24f3fcc73ecb7bff17fcbe029b799c6624
        # save the config file to linux build tree
        mkdir build_dir
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-11.2.0 make.cross O=build_dir ARCH=arc SHELL=/bin/bash net/smc/

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@intel.com>

All warnings (new ones prefixed by >>):

   net/smc/af_smc.c: In function 'smc_listen':
>> net/smc/af_smc.c:2202:25: warning: assignment discards 'const' qualifier from pointer target type [-Wdiscarded-qualifiers]
    2202 |         smc->ori_af_ops = inet_csk(smc->clcsock->sk)->icsk_af_ops;
         |                         ^


vim +/const +2202 net/smc/af_smc.c

  2166	
  2167	static int smc_listen(struct socket *sock, int backlog)
  2168	{
  2169		struct sock *sk = sock->sk;
  2170		struct smc_sock *smc;
  2171		int rc;
  2172	
  2173		smc = smc_sk(sk);
  2174		lock_sock(sk);
  2175	
  2176		rc = -EINVAL;
  2177		if ((sk->sk_state != SMC_INIT && sk->sk_state != SMC_LISTEN) ||
  2178		    smc->connect_nonblock)
  2179			goto out;
  2180	
  2181		rc = 0;
  2182		if (sk->sk_state == SMC_LISTEN) {
  2183			sk->sk_max_ack_backlog = backlog;
  2184			goto out;
  2185		}
  2186		/* some socket options are handled in core, so we could not apply
  2187		 * them to the clc socket -- copy smc socket options to clc socket
  2188		 */
  2189		smc_copy_sock_settings_to_clc(smc);
  2190		if (!smc->use_fallback)
  2191			tcp_sk(smc->clcsock->sk)->syn_smc = 1;
  2192	
  2193		/* save original sk_data_ready function and establish
  2194		 * smc-specific sk_data_ready function
  2195		 */
  2196		smc->clcsk_data_ready = smc->clcsock->sk->sk_data_ready;
  2197		smc->clcsock->sk->sk_data_ready = smc_clcsock_data_ready;
  2198		smc->clcsock->sk->sk_user_data =
  2199			(void *)((uintptr_t)smc | SK_USER_DATA_NOCOPY);
  2200	
  2201		/* save origin ops */
> 2202		smc->ori_af_ops = inet_csk(smc->clcsock->sk)->icsk_af_ops;
  2203	
  2204		smc->af_ops = *smc->ori_af_ops;
  2205		smc->af_ops.syn_recv_sock = smc_tcp_syn_recv_sock;
  2206	
  2207		inet_csk(smc->clcsock->sk)->icsk_af_ops = &smc->af_ops;
  2208	
  2209		rc = kernel_listen(smc->clcsock, backlog);
  2210		if (rc) {
  2211			smc->clcsock->sk->sk_data_ready = smc->clcsk_data_ready;
  2212			goto out;
  2213		}
  2214		sk->sk_max_ack_backlog = backlog;
  2215		sk->sk_ack_backlog = 0;
  2216		sk->sk_state = SMC_LISTEN;
  2217	
  2218	out:
  2219		release_sock(sk);
  2220		return rc;
  2221	}
  2222	

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org
kernel test robot Jan. 27, 2022, 3:52 p.m. UTC | #2 
Hi Wythe",

Thank you for the patch! Yet something to improve:

[auto build test ERROR on net-next/master]

url:    https://github.com/0day-ci/linux/commits/D-Wythe/Optimizing-performance-in-short-lived/20220127-200912
base:   https://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next.git fbb8295248e1d6f576d444309fcf79356008eac1
config: mips-buildonly-randconfig-r004-20220124 (https://download.01.org/0day-ci/archive/20220127/202201272328.JtsPKLkq-lkp@intel.com/config)
compiler: clang version 14.0.0 (https://github.com/llvm/llvm-project f32dccb9a43b02ce4e540d6ba5dbbdb188f2dc7d)
reproduce (this is a W=1 build):
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # install mips cross compiling tool for clang build
        # apt-get install binutils-mips-linux-gnu
        # https://github.com/0day-ci/linux/commit/718aff24f3fcc73ecb7bff17fcbe029b799c6624
        git remote add linux-review https://github.com/0day-ci/linux
        git fetch --no-tags linux-review D-Wythe/Optimizing-performance-in-short-lived/20220127-200912
        git checkout 718aff24f3fcc73ecb7bff17fcbe029b799c6624
        # save the config file to linux build tree
        mkdir build_dir
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=mips SHELL=/bin/bash arch/mips/kernel/ net/smc/

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@intel.com>

All errors (new ones prefixed by >>):

>> net/smc/af_smc.c:2202:18: error: assigning to 'struct inet_connection_sock_af_ops *' from 'const struct inet_connection_sock_af_ops *' discards qualifiers [-Werror,-Wincompatible-pointer-types-discards-qualifiers]
           smc->ori_af_ops = inet_csk(smc->clcsock->sk)->icsk_af_ops;
                           ^ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   1 error generated.


vim +2202 net/smc/af_smc.c

  2166	
  2167	static int smc_listen(struct socket *sock, int backlog)
  2168	{
  2169		struct sock *sk = sock->sk;
  2170		struct smc_sock *smc;
  2171		int rc;
  2172	
  2173		smc = smc_sk(sk);
  2174		lock_sock(sk);
  2175	
  2176		rc = -EINVAL;
  2177		if ((sk->sk_state != SMC_INIT && sk->sk_state != SMC_LISTEN) ||
  2178		    smc->connect_nonblock)
  2179			goto out;
  2180	
  2181		rc = 0;
  2182		if (sk->sk_state == SMC_LISTEN) {
  2183			sk->sk_max_ack_backlog = backlog;
  2184			goto out;
  2185		}
  2186		/* some socket options are handled in core, so we could not apply
  2187		 * them to the clc socket -- copy smc socket options to clc socket
  2188		 */
  2189		smc_copy_sock_settings_to_clc(smc);
  2190		if (!smc->use_fallback)
  2191			tcp_sk(smc->clcsock->sk)->syn_smc = 1;
  2192	
  2193		/* save original sk_data_ready function and establish
  2194		 * smc-specific sk_data_ready function
  2195		 */
  2196		smc->clcsk_data_ready = smc->clcsock->sk->sk_data_ready;
  2197		smc->clcsock->sk->sk_data_ready = smc_clcsock_data_ready;
  2198		smc->clcsock->sk->sk_user_data =
  2199			(void *)((uintptr_t)smc | SK_USER_DATA_NOCOPY);
  2200	
  2201		/* save origin ops */
> 2202		smc->ori_af_ops = inet_csk(smc->clcsock->sk)->icsk_af_ops;
  2203	
  2204		smc->af_ops = *smc->ori_af_ops;
  2205		smc->af_ops.syn_recv_sock = smc_tcp_syn_recv_sock;
  2206	
  2207		inet_csk(smc->clcsock->sk)->icsk_af_ops = &smc->af_ops;
  2208	
  2209		rc = kernel_listen(smc->clcsock, backlog);
  2210		if (rc) {
  2211			smc->clcsock->sk->sk_data_ready = smc->clcsk_data_ready;
  2212			goto out;
  2213		}
  2214		sk->sk_max_ack_backlog = backlog;
  2215		sk->sk_ack_backlog = 0;
  2216		sk->sk_state = SMC_LISTEN;
  2217	
  2218	out:
  2219		release_sock(sk);
  2220		return rc;
  2221	}
  2222	

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org
kernel test robot Jan. 27, 2022, 11:23 p.m. UTC | #3 
Hi Wythe",

Thank you for the patch! Perhaps something to improve:

[auto build test WARNING on net-next/master]

url:    https://github.com/0day-ci/linux/commits/D-Wythe/Optimizing-performance-in-short-lived/20220127-200912
base:   https://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next.git fbb8295248e1d6f576d444309fcf79356008eac1
config: x86_64-randconfig-s022-20220124 (https://download.01.org/0day-ci/archive/20220128/202201280741.2EsIf9Jy-lkp@intel.com/config)
compiler: gcc-9 (Debian 9.3.0-22) 9.3.0
reproduce:
        # apt-get install sparse
        # sparse version: v0.6.4-dirty
        # https://github.com/0day-ci/linux/commit/718aff24f3fcc73ecb7bff17fcbe029b799c6624
        git remote add linux-review https://github.com/0day-ci/linux
        git fetch --no-tags linux-review D-Wythe/Optimizing-performance-in-short-lived/20220127-200912
        git checkout 718aff24f3fcc73ecb7bff17fcbe029b799c6624
        # save the config file to linux build tree
        mkdir build_dir
        make W=1 C=1 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__' O=build_dir ARCH=x86_64 SHELL=/bin/bash net/smc/

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@intel.com>


sparse warnings: (new ones prefixed by >>)
>> net/smc/af_smc.c:2202:25: sparse: sparse: incorrect type in assignment (different modifiers) @@     expected struct inet_connection_sock_af_ops *ori_af_ops @@     got struct inet_connection_sock_af_ops const *icsk_af_ops @@
   net/smc/af_smc.c:2202:25: sparse:     expected struct inet_connection_sock_af_ops *ori_af_ops
   net/smc/af_smc.c:2202:25: sparse:     got struct inet_connection_sock_af_ops const *icsk_af_ops

vim +2202 net/smc/af_smc.c

  2166	
  2167	static int smc_listen(struct socket *sock, int backlog)
  2168	{
  2169		struct sock *sk = sock->sk;
  2170		struct smc_sock *smc;
  2171		int rc;
  2172	
  2173		smc = smc_sk(sk);
  2174		lock_sock(sk);
  2175	
  2176		rc = -EINVAL;
  2177		if ((sk->sk_state != SMC_INIT && sk->sk_state != SMC_LISTEN) ||
  2178		    smc->connect_nonblock)
  2179			goto out;
  2180	
  2181		rc = 0;
  2182		if (sk->sk_state == SMC_LISTEN) {
  2183			sk->sk_max_ack_backlog = backlog;
  2184			goto out;
  2185		}
  2186		/* some socket options are handled in core, so we could not apply
  2187		 * them to the clc socket -- copy smc socket options to clc socket
  2188		 */
  2189		smc_copy_sock_settings_to_clc(smc);
  2190		if (!smc->use_fallback)
  2191			tcp_sk(smc->clcsock->sk)->syn_smc = 1;
  2192	
  2193		/* save original sk_data_ready function and establish
  2194		 * smc-specific sk_data_ready function
  2195		 */
  2196		smc->clcsk_data_ready = smc->clcsock->sk->sk_data_ready;
  2197		smc->clcsock->sk->sk_data_ready = smc_clcsock_data_ready;
  2198		smc->clcsock->sk->sk_user_data =
  2199			(void *)((uintptr_t)smc | SK_USER_DATA_NOCOPY);
  2200	
  2201		/* save origin ops */
> 2202		smc->ori_af_ops = inet_csk(smc->clcsock->sk)->icsk_af_ops;
  2203	
  2204		smc->af_ops = *smc->ori_af_ops;
  2205		smc->af_ops.syn_recv_sock = smc_tcp_syn_recv_sock;
  2206	
  2207		inet_csk(smc->clcsock->sk)->icsk_af_ops = &smc->af_ops;
  2208	
  2209		rc = kernel_listen(smc->clcsock, backlog);
  2210		if (rc) {
  2211			smc->clcsock->sk->sk_data_ready = smc->clcsk_data_ready;
  2212			goto out;
  2213		}
  2214		sk->sk_max_ack_backlog = backlog;
  2215		sk->sk_ack_backlog = 0;
  2216		sk->sk_state = SMC_LISTEN;
  2217	
  2218	out:
  2219		release_sock(sk);
  2220		return rc;
  2221	}
  2222	

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org
diff mbox series

Patch

diff --git a/net/smc/af_smc.c b/net/smc/af_smc.c
index 1b40304..66a0e64 100644
--- a/net/smc/af_smc.c
+++ b/net/smc/af_smc.c
@@ -73,6 +73,34 @@  static void smc_set_keepalive(struct sock *sk, int val)
 	smc->clcsock->sk->sk_prot->keepalive(smc->clcsock->sk, val);
 }
 
+static struct sock *smc_tcp_syn_recv_sock(const struct sock *sk, struct sk_buff *skb,
+					  struct request_sock *req,
+					  struct dst_entry *dst,
+					  struct request_sock *req_unhash,
+					  bool *own_req)
+{
+	struct smc_sock *smc;
+
+	smc = (struct smc_sock *)((uintptr_t)sk->sk_user_data & ~SK_USER_DATA_NOCOPY);
+
+	if (READ_ONCE(sk->sk_ack_backlog) + atomic_read(&smc->smc_pendings) >
+				sk->sk_max_ack_backlog)
+		goto drop;
+
+	if (sk_acceptq_is_full(&smc->sk)) {
+		NET_INC_STATS(sock_net(sk), LINUX_MIB_LISTENOVERFLOWS);
+		goto drop;
+	}
+
+	/* passthrough to origin syn recv sock fct */
+	return smc->ori_af_ops->syn_recv_sock(sk, skb, req, dst, req_unhash, own_req);
+
+drop:
+	dst_release(dst);
+	tcp_listendrop(sk);
+	return NULL;
+}
+
 static struct smc_hashinfo smc_v4_hashinfo = {
 	.lock = __RW_LOCK_UNLOCKED(smc_v4_hashinfo.lock),
 };
@@ -1491,6 +1519,9 @@  static void smc_listen_out(struct smc_sock *new_smc)
 	struct smc_sock *lsmc = new_smc->listen_smc;
 	struct sock *newsmcsk = &new_smc->sk;
 
+	if (tcp_sk(new_smc->clcsock->sk)->syn_smc)
+		atomic_dec(&lsmc->smc_pendings);
+
 	if (lsmc->sk.sk_state == SMC_LISTEN) {
 		lock_sock_nested(&lsmc->sk, SINGLE_DEPTH_NESTING);
 		smc_accept_enqueue(&lsmc->sk, newsmcsk);
@@ -2096,6 +2127,9 @@  static void smc_tcp_listen_work(struct work_struct *work)
 		if (!new_smc)
 			continue;
 
+		if (tcp_sk(new_smc->clcsock->sk)->syn_smc)
+			atomic_inc(&lsmc->smc_pendings);
+
 		new_smc->listen_smc = lsmc;
 		new_smc->use_fallback = lsmc->use_fallback;
 		new_smc->fallback_rsn = lsmc->fallback_rsn;
@@ -2163,6 +2197,15 @@  static int smc_listen(struct socket *sock, int backlog)
 	smc->clcsock->sk->sk_data_ready = smc_clcsock_data_ready;
 	smc->clcsock->sk->sk_user_data =
 		(void *)((uintptr_t)smc | SK_USER_DATA_NOCOPY);
+
+	/* save origin ops */
+	smc->ori_af_ops = inet_csk(smc->clcsock->sk)->icsk_af_ops;
+
+	smc->af_ops = *smc->ori_af_ops;
+	smc->af_ops.syn_recv_sock = smc_tcp_syn_recv_sock;
+
+	inet_csk(smc->clcsock->sk)->icsk_af_ops = &smc->af_ops;
+
 	rc = kernel_listen(smc->clcsock, backlog);
 	if (rc) {
 		smc->clcsock->sk->sk_data_ready = smc->clcsk_data_ready;
diff --git a/net/smc/smc.h b/net/smc/smc.h
index bd2f3dc..4366f24 100644
--- a/net/smc/smc.h
+++ b/net/smc/smc.h
@@ -240,6 +240,10 @@  struct smc_sock {				/* smc sock container */
 	bool			use_fallback;	/* fallback to tcp */
 	int			fallback_rsn;	/* reason for fallback */
 	u32			peer_diagnosis; /* decline reason from peer */
+	atomic_t                smc_pendings;   /* pending smc connections */
+	struct inet_connection_sock_af_ops	af_ops;
+	struct inet_connection_sock_af_ops	*ori_af_ops;
+						/* origin af ops */
 	int			sockopt_defer_accept;
 						/* sockopt TCP_DEFER_ACCEPT
 						 * value