Hi,
This patch introduces a new sysctl option to make IPv4 Address Scoping
configurable <draft-stewart-tsvwg-sctp-ipv4-00.txt>.
In networking environments where DNAT rules in prerouting chains convert dest
IP's to link-local/private IP addresses, SCTP connections fail to establish
as the INIT chunk is dropped by the kernel due to address scope match failure.
For example to support overlapping IP addresses a Layer-5 application listens
on link local IP's, and there is a DNAT rule that maps the dest IP to a link
local IP. Such applications never get the SCTP INIT if the address-scoping draft
is strictly followed.
This sysctl configuration allows SCTP to function in such unconventional
networking environments.
Sysctl options:
0 - Disable IPv4 address scoping draft altogether
1 - Enable IPv4 address scoping (default, current behavior)
2 - Enable address scoping but allow IPv4 private addresses (as
defined in draft)
3 - Enable address scoping but allow IPv4 link local address (as
defined in draft)
Regards,
Bhaskar
Patch generated against kernel 2.6.31-rc7.
Signed-off-by: Bhaskar Dutta <bhaskar.dutta@xxxxxxxxxxxxxxx>
---
Documentation/networking/ip-sysctl.txt | 10 ++++++++++
include/linux/sysctl.h | 1 +
include/net/sctp/constants.h | 7 +++++++
include/net/sctp/structs.h | 11 +++++++++++
kernel/sysctl_check.c | 1 +
net/sctp/bind_addr.c | 19 +++++++++++++++++++
net/sctp/protocol.c | 11 ++++++-----
net/sctp/sysctl.c | 12 ++++++++++++
8 files changed, 67 insertions(+), 5 deletions(-)
diff --git a/Documentation/networking/ip-sysctl.txt
b/Documentation/networking/ip-sysctl.txt
index 8be7623..da07602 100644
--- a/Documentation/networking/ip-sysctl.txt
+++ b/Documentation/networking/ip-sysctl.txt
@@ -1282,6 +1282,16 @@ sctp_rmem - vector of 3 INTEGERs: min, default, max
sctp_wmem - vector of 3 INTEGERs: min, default, max
See tcp_wmem for a description.
+addr_scope_policy - INTEGER
+ Control IPv4 address scoping - draft-stewart-tsvwg-sctp-ipv4-00
+
+ 0 - Disable IPv4 address scoping
+ 1 - Enable IPv4 address scoping
+ 2 - Follow draft but allow IPv4 private addresses
+ 3 - Follow draft but allow IPv4 link local addresses
+
+ Default: 1
+
/proc/sys/net/core/*
dev_weight - INTEGER
diff --git a/include/linux/sysctl.h b/include/linux/sysctl.h
index e76d3b2..5f3db20 100644
--- a/include/linux/sysctl.h
+++ b/include/linux/sysctl.h
@@ -779,6 +779,7 @@ enum {
NET_SCTP_SNDBUF_POLICY = 15,
NET_SCTP_SACK_TIMEOUT = 16,
NET_SCTP_RCVBUF_POLICY = 17,
+ NET_SCTP_SCOPE_POLICY = 18,
};
/* /proc/sys/net/bridge */
diff --git a/include/net/sctp/constants.h b/include/net/sctp/constants.h
index b05b055..699e6ae 100644
--- a/include/net/sctp/constants.h
+++ b/include/net/sctp/constants.h
@@ -361,6 +361,13 @@ typedef enum {
SCTP_SCOPE_UNUSABLE, /* IPv4 unusable addresses */
} sctp_scope_t;
+typedef enum {
+ SCTP_SCOPE_POLICY_DISABLE, /* Disable IPv4 address scoping */
+ SCTP_SCOPE_POLICY_ENABLE, /* Enable IPv4 address scoping */
+ SCTP_SCOPE_POLICY_PRIVATE, /* Follow draft but allow IPv4 private addresses */
+ SCTP_SCOPE_POLICY_LINK, /* Follow draft but allow IPv4 link local
addresses */
+} sctp_scope_policy_t;
+
/* Based on IPv4 scoping <draft-stewart-tsvwg-sctp-ipv4-00.txt>,
* SCTP IPv4 unusable addresses: 0.0.0.0/8, 224.0.0.0/4, 198.18.0.0/24,
* 192.88.99.0/24.
diff --git a/include/net/sctp/structs.h b/include/net/sctp/structs.h
index edfcacf..547fbb1 100644
--- a/include/net/sctp/structs.h
+++ b/include/net/sctp/structs.h
@@ -219,6 +219,16 @@ extern struct sctp_globals {
/* Flag to idicate if SCTP-AUTH is enabled */
int auth_enable;
+ /*
+ * Policy to control SCTP IPv4 address scoping
+ * 0 - Disable IPv4 address scoping
+ * 1 - Enable IPv4 address scoping
+ * 2 - Selectively allow only IPv4 private addresses
+ * 3 - Selectively allow only IPv4 link local address
+ */
+ int ipv4_scope_policy;
+
+
/* Flag to indicate whether computing and verifying checksum
* is disabled. */
int checksum_disable;
@@ -252,6 +262,7 @@ extern struct sctp_globals {
#define sctp_port_hashtable (sctp_globals.port_hashtable)
#define sctp_local_addr_list (sctp_globals.local_addr_list)
#define sctp_local_addr_lock (sctp_globals.addr_list_lock)
+#define sctp_scope_policy (sctp_globals.ipv4_scope_policy)
#define sctp_addip_enable (sctp_globals.addip_enable)
#define sctp_addip_noauth (sctp_globals.addip_noauth_enable)
#define sctp_prsctp_enable (sctp_globals.prsctp_enable)
diff --git a/kernel/sysctl_check.c b/kernel/sysctl_check.c
index b38423c..6a813a4 100644
--- a/kernel/sysctl_check.c
+++ b/kernel/sysctl_check.c
@@ -604,6 +604,7 @@ static const struct trans_ctl_table
trans_net_sctp_table[] = {
{ NET_SCTP_SNDBUF_POLICY, "sndbuf_policy" },
{ NET_SCTP_SACK_TIMEOUT, "sack_timeout" },
{ NET_SCTP_RCVBUF_POLICY, "rcvbuf_policy" },
+ { NET_SCTP_SCOPE_POLICY, "addr_scope_policy" },
{}
};
diff --git a/net/sctp/bind_addr.c b/net/sctp/bind_addr.c
index 6d5944a..6d8e0b0 100644
--- a/net/sctp/bind_addr.c
+++ b/net/sctp/bind_addr.c
@@ -510,9 +510,28 @@ int sctp_in_scope(const union sctp_addr *addr,
sctp_scope_t scope)
* of requested destination address, sender and receiver
* SHOULD include all of its addresses with level greater
* than or equal to L.
+ *
+ * Address scoping can be selectively controlled via sysctl
+ * option
*/
+ switch (sctp_scope_policy) {
+ case SCTP_SCOPE_POLICY_DISABLE:
+ return 1;
+ case SCTP_SCOPE_POLICY_ENABLE:
if (addr_scope <= scope)
return 1;
+ break;
+ case SCTP_SCOPE_POLICY_PRIVATE:
+ if (addr_scope <= scope || SCTP_SCOPE_PRIVATE == addr_scope)
+ return 1;
+ break;
+ case SCTP_SCOPE_POLICY_LINK:
+ if (addr_scope <= scope || SCTP_SCOPE_LINK == addr_scope)
+ return 1;
+ break;
+ default:
+ break;
+ }
return 0;
}
diff --git a/net/sctp/protocol.c b/net/sctp/protocol.c
index a76da65..5c65cac 100644
--- a/net/sctp/protocol.c
+++ b/net/sctp/protocol.c
@@ -431,16 +431,14 @@ static int sctp_v4_available(union sctp_addr
*addr, struct sctp_sock *sp)
* of requested destination address, sender and receiver
* SHOULD include all of its addresses with level greater
* than or equal to L.
+ *
+ * IPv4 scoping can be controlled through sysctl option
+ * net.sctp.addr_scope_policy
*/
static sctp_scope_t sctp_v4_scope(union sctp_addr *addr)
{
sctp_scope_t retval;
- /* Should IPv4 scoping be a sysctl configurable option
- * so users can turn it off (default on) for certain
- * unconventional networking environments?
- */
-
/* Check for unusable SCTP addresses. */
if (IS_IPV4_UNUSABLE_ADDRESS(addr->v4.sin_addr.s_addr)) {
retval = SCTP_SCOPE_UNUSABLE;
@@ -1259,6 +1257,9 @@ SCTP_STATIC __init int sctp_init(void)
/* Disable AUTH by default. */
sctp_auth_enable = 0;
+ /* Set SCOPE policy to enabled */
+ sctp_scope_policy = SCTP_SCOPE_POLICY_ENABLE;
+
sctp_sysctl_register();
INIT_LIST_HEAD(&sctp_address_families);
diff --git a/net/sctp/sysctl.c b/net/sctp/sysctl.c
index 63eabbc..9f1b412 100644
--- a/net/sctp/sysctl.c
+++ b/net/sctp/sysctl.c
@@ -51,6 +51,7 @@ static int timer_max = 86400000; /* ms in one day */
static int int_max = INT_MAX;
static int sack_timer_min = 1;
static int sack_timer_max = 500;
+static int addr_scope_max = 3; /* check sctp_scope_policy_t in
include/net/sctp/constants.h for max entries */
extern int sysctl_sctp_mem[3];
extern int sysctl_sctp_rmem[3];
@@ -272,6 +273,17 @@ static ctl_table sctp_table[] = {
.proc_handler = proc_dointvec,
.strategy = sysctl_intvec
},
+ {
+ .ctl_name = NET_SCTP_SCOPE_POLICY,
+ .procname = "addr_scope_policy",
+ .data = &sctp_scope_policy,
+ .maxlen = sizeof(int),
+ .mode = 0644,
+ .proc_handler = &proc_dointvec_minmax,
+ .strategy = &sysctl_intvec,
+ .extra1 = &zero,
+ .extra2 = &addr_scope_max,
+ },
{ .ctl_name = 0 }
};
--
1.6.2.4
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