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Subject[Patch 3/3] net: reserve ports for applications using fixed port numbers

(Dropped the infiniband part, because Tetsuo modified the related code,
I will send a separate patch for it once this is accepted.)

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 <opurdila@ixiacom.com>
Signed-off-by: WANG Cong <amwang@redhat.com>
Cc: Neil Horman <nhorman@tuxdriver.com>
Cc: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Eric W. Biederman <ebiederm@xmission.com>
---
Index: linux-2.6/Documentation/networking/ip-sysctl.txt
===================================================================
--- linux-2.6.orig/Documentation/networking/ip-sysctl.txt
+++ linux-2.6/Documentation/networking/ip-sysctl.txt
@@ -588,6 +588,37 @@ 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.
+
+ Note that ip_local_port_range and ip_local_reserved_ports
+ settings are independent and both are considered by the kernel
+ when determining which ports are available for automatic port
+ assignments.
+
+ You can reserve ports which are not in the current
+ ip_local_port_range, e.g.:
+
+ $ cat /proc/sys/net/ipv4/ip_local_port_range
+ 32000 61000
+ $ cat /proc/sys/net/ipv4/ip_local_reserved_ports
+ 8080,9148
+
+ although this is redundant. However such a setting is useful
+ if later the port range is changed to a value that will
+ include the reserved ports.
+
+ 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.
Index: linux-2.6/include/net/ip.h
===================================================================
--- linux-2.6.orig/include/net/ip.h
+++ linux-2.6/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;

Index: linux-2.6/net/ipv4/af_inet.c
===================================================================
--- linux-2.6.orig/net/ipv4/af_inet.c
+++ linux-2.6/net/ipv4/af_inet.c
@@ -1552,9 +1552,13 @@ 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)
@@ -1653,6 +1657,8 @@ 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;
}

Index: linux-2.6/net/ipv4/inet_connection_sock.c
===================================================================
--- linux-2.6.orig/net/ipv4/inet_connection_sock.c
+++ linux-2.6/net/ipv4/inet_connection_sock.c
@@ -37,6 +37,9 @@ struct local_ports sysctl_local_ports __
.range = { 32768, 61000 },
};

+unsigned long *sysctl_local_reserved_ports;
+EXPORT_SYMBOL(sysctl_local_reserved_ports);
+
void inet_get_local_port_range(int *low, int *high)
{
unsigned seq;
@@ -112,6 +115,8 @@ again:

smallest_size = -1;
do {
+ if (inet_is_reserved_local_port(rover))
+ goto next_nolock;
head = &hashinfo->bhash[inet_bhashfn(net, rover,
hashinfo->bhash_size)];
spin_lock(&head->lock);
@@ -136,6 +141,7 @@ again:
break;
next:
spin_unlock(&head->lock);
+ next_nolock:
if (++rover > high)
rover = low;
} while (--remaining > 0);
Index: linux-2.6/net/ipv4/inet_hashtables.c
===================================================================
--- linux-2.6.orig/net/ipv4/inet_hashtables.c
+++ linux-2.6/net/ipv4/inet_hashtables.c
@@ -456,6 +456,8 @@ int __inet_hash_connect(struct inet_time
local_bh_disable();
for (i = 1; i <= remaining; i++) {
port = low + (i + offset) % remaining;
+ if (inet_is_reserved_local_port(port))
+ continue;
head = &hinfo->bhash[inet_bhashfn(net, port,
hinfo->bhash_size)];
spin_lock(&head->lock);
Index: linux-2.6/net/ipv4/sysctl_net_ipv4.c
===================================================================
--- linux-2.6.orig/net/ipv4/sysctl_net_ipv4.c
+++ linux-2.6/net/ipv4/sysctl_net_ipv4.c
@@ -299,6 +299,13 @@ static struct ctl_table ipv4_table[] = {
.mode = 0644,
.proc_handler = ipv4_local_port_range,
},
+ {
+ .procname = "ip_local_reserved_ports",
+ .data = NULL, /* initialized in sysctl_ipv4_init */
+ .maxlen = 65536,
+ .mode = 0644,
+ .proc_handler = proc_do_large_bitmap,
+ },
#ifdef CONFIG_IP_MULTICAST
{
.procname = "igmp_max_memberships",
@@ -736,6 +743,16 @@ static __net_initdata struct pernet_oper
static __init int sysctl_ipv4_init(void)
{
struct ctl_table_header *hdr;
+ struct ctl_table *i;
+
+ for (i = ipv4_table; i->procname; i++) {
+ if (strcmp(i->procname, "ip_local_reserved_ports") == 0) {
+ i->data = sysctl_local_reserved_ports;
+ break;
+ }
+ }
+ if (!i->procname)
+ return -EINVAL;

hdr = register_sysctl_paths(net_ipv4_ctl_path, ipv4_table);
if (hdr == NULL)
Index: linux-2.6/net/ipv4/udp.c
===================================================================
--- linux-2.6.orig/net/ipv4/udp.c
+++ linux-2.6/net/ipv4/udp.c
@@ -233,7 +233,8 @@ int udp_lib_get_port(struct sock *sk, un
*/
do {
if (low <= snum && snum <= high &&
- !test_bit(snum >> udptable->log, bitmap))
+ !test_bit(snum >> udptable->log, bitmap) &&
+ !inet_is_reserved_local_port(snum))
goto found;
snum += rand;
} while (snum != first);
Index: linux-2.6/net/sctp/socket.c
===================================================================
--- linux-2.6.orig/net/sctp/socket.c
+++ linux-2.6/net/sctp/socket.c
@@ -5436,6 +5436,8 @@ static long sctp_get_port_local(struct s
rover++;
if ((rover < low) || (rover > high))
rover = low;
+ if (inet_is_reserved_local_port(rover))
+ continue;
index = sctp_phashfn(rover);
head = &sctp_port_hashtable[index];
sctp_spin_lock(&head->lock);

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