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>
Signed-off-by: David S. Miller <davem@davemloft.net>

8 files changed, 73 insertions, 2 deletions

diff --git a/Documentation/networking/ip-sysctl.txt b/Documentation/networking/ip-sysctl.txt
index 8b72c88ba213..d0536b5a4e01 100644
--- a/Documentation/networking/ip-sysctl.txt
+++ b/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.
diff --git a/include/net/ip.h b/include/net/ip.h
index 8149b77cea9b..63548f0a44b1 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 c6c43bcd1c6f..551ce564b035 100644
--- a/net/ipv4/af_inet.c
+++ b/net/ipv4/af_inet.c
@@ -1573,9 +1573,13 @@ 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)
@@ -1674,6 +1678,8 @@ 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 e0a3e3537b14..70eb3507c406 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);
+
 void inet_get_local_port_range(int *low, int *high)
 {
         unsigned seq;
@@ -108,6 +111,8 @@ 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);
@@ -130,6 +135,7 @@ again:
                         break;
                 next:
                         spin_unlock(&head->lock);
+                next_nolock:
                         if (++rover > high)
                                 rover = low;
                 } while (--remaining > 0);
diff --git a/net/ipv4/inet_hashtables.c b/net/ipv4/inet_hashtables.c
index 2b79377b468d..d3e160a88219 100644
--- a/net/ipv4/inet_hashtables.c
+++ b/net/ipv4/inet_hashtables.c
@@ -456,6 +456,8 @@ int __inet_hash_connect(struct inet_timewait_death_row *death_row,
                 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);
diff --git a/net/ipv4/sysctl_net_ipv4.c b/net/ipv4/sysctl_net_ipv4.c
index 1cd5c15174b8..d96c1da4b17c 100644
--- a/net/ipv4/sysctl_net_ipv4.c
+++ b/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_operations ipv4_sysctl_ops = {
 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)
diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index f3e00c5cd1ed..9de6a698f91d 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -233,7 +233,8 @@ int udp_lib_get_port(struct sock *sk, unsigned short snum,
                          */
                         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);
diff --git a/net/sctp/socket.c b/net/sctp/socket.c
index ba1add0b13c3..ca44917872d2 100644
--- a/net/sctp/socket.c
+++ b/net/sctp/socket.c
@@ -5433,6 +5433,8 @@ static long sctp_get_port_local(struct sock *sk, union sctp_addr *addr)
                         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);