Re: [net-next PATCH v5 3/3] net: reserve ports for applications using fixed port numbers

This patch introduces /proc/sys/net/ipv4/ip_local_reserved_ports which
allows users to reserve ports for third-party applications.

The reserved ports will not be used by automatic port assignments
(e.g. when calling connect() or bind() with port number 0). Explicit
port allocation behavior is unchanged.

Signed-off-by: Octavian Purdila <redacted>
Signed-off-by: WANG Cong <redacted>
Cc: Neil Horman <nhorman@tuxdriver.com>
Cc: Eric Dumazet <redacted>
Cc: Eric W. Biederman <redacted>
---
 Documentation/networking/ip-sysctl.txt |   14 ++++++++++++++
 drivers/infiniband/core/cma.c          |    7 ++++++-
 include/net/ip.h                       |    6 ++++++
 net/ipv4/af_inet.c                     |    8 +++++++-
 net/ipv4/inet_connection_sock.c        |    6 ++++++
 net/ipv4/inet_hashtables.c             |    2 ++
 net/ipv4/sysctl_net_ipv4.c             |   17 +++++++++++++++++
 net/ipv4/udp.c                         |    3 ++-
 net/sctp/socket.c                      |    2 ++
 9 files changed, 62 insertions(+), 3 deletions(-)

diff --git a/Documentation/networking/ip-sysctl.txt b/Documentation/networking/ip-sysctl.txt
index 2dc7a1d..6534ee7 100644
--- a/Documentation/networking/ip-sysctl.txt
+++ b/Documentation/networking/ip-sysctl.txt

@@ -564,6 +564,20 @@ ip_local_port_range - 2 INTEGERS
 	(i.e. by default) range 1024-4999 is enough to issue up to
 	2000 connections per second to systems supporting timestamps.
 
+ip_local_reserved_ports - list of comma separated ranges
+	Specify the ports which are reserved for known third-party
+	applications. These ports will not be used by automatic port
+	assignments (e.g. when calling connect() or bind() with port
+	number 0). Explicit port allocation behavior is unchanged.
+
+	The format used for both input and output is a comma separated
+	list of ranges (e.g. "1,2-4,10-10" for ports 1, 2, 3, 4 and
+	10). Writing to the file will clear all previously reserved
+	ports and update the current list with the one given in the
+	input.
+
+	Default: Empty
+
 ip_nonlocal_bind - BOOLEAN
 	If set, allows processes to bind() to non-local IP addresses,
 	which can be quite useful - but may break some applications.

diff --git a/drivers/infiniband/core/cma.c b/drivers/infiniband/core/cma.c
index 875e34e..06c9fa5 100644
--- a/drivers/infiniband/core/cma.c
+++ b/drivers/infiniband/core/cma.c

@@ -1979,6 +1979,8 @@ retry:
 	/* FIXME: add proper port randomization per like inet_csk_get_port */
 	do {
 		ret = idr_get_new_above(ps, bind_list, next_port, &port);
+		if (inet_is_reserved_local_port(port))
+			ret = -EAGAIN;
 	} while ((ret == -EAGAIN) && idr_pre_get(ps, GFP_KERNEL));
 
 	if (ret)

@@ -2995,10 +2997,13 @@ static int __init cma_init(void)
 {
 	int ret, low, high, remaining;
 
-	get_random_bytes(&next_port, sizeof next_port);
 	inet_get_local_port_range(&low, &high);
+again:
+	get_random_bytes(&next_port, sizeof next_port);
 	remaining = (high - low) + 1;
 	next_port = ((unsigned int) next_port % remaining) + low;
+	if (inet_is_reserved_local_port(next_port))
+		goto again;
 
 	cma_wq = create_singlethread_workqueue("rdma_cm");
 	if (!cma_wq)

diff --git a/include/net/ip.h b/include/net/ip.h
index 503994a..3da9004 100644
--- a/include/net/ip.h
+++ b/include/net/ip.h

@@ -184,6 +184,12 @@ extern struct local_ports {
 } sysctl_local_ports;
 extern void inet_get_local_port_range(int *low, int *high);
 
+extern unsigned long *sysctl_local_reserved_ports;
+static inline int inet_is_reserved_local_port(int port)
+{
+	return test_bit(port, sysctl_local_reserved_ports);
+}
+
 extern int sysctl_ip_default_ttl;
 extern int sysctl_ip_nonlocal_bind;
 

diff --git a/net/ipv4/af_inet.c b/net/ipv4/af_inet.c
index 33b7dff..e283fbe 100644
--- a/net/ipv4/af_inet.c
+++ b/net/ipv4/af_inet.c

@@ -1546,9 +1546,13 @@ static int __init inet_init(void)
 
 	BUILD_BUG_ON(sizeof(struct inet_skb_parm) > sizeof(dummy_skb->cb));
 
+	sysctl_local_reserved_ports = kzalloc(65536 / 8, GFP_KERNEL);
+	if (!sysctl_local_reserved_ports)
+		goto out;
+
 	rc = proto_register(&tcp_prot, 1);
 	if (rc)
-		goto out;
+		goto out_free_reserved_ports;
 
 	rc = proto_register(&udp_prot, 1);
 	if (rc)

@@ -1647,6 +1651,8 @@ out_unregister_udp_proto:
 	proto_unregister(&udp_prot);
 out_unregister_tcp_proto:
 	proto_unregister(&tcp_prot);
+out_free_reserved_ports:
+	kfree(sysctl_local_reserved_ports);
 	goto out;
 }
 

diff --git a/net/ipv4/inet_connection_sock.c b/net/ipv4/inet_connection_sock.c
index 8da6429..1acb462 100644
--- a/net/ipv4/inet_connection_sock.c
+++ b/net/ipv4/inet_connection_sock.c

@@ -37,6 +37,9 @@ struct local_ports sysctl_local_ports __read_mostly = {
 	.range = { 32768, 61000 },
 };
 
+unsigned long *sysctl_local_reserved_ports;
+EXPORT_SYMBOL(sysctl_local_reserved_ports);
+