Bhaskar Dutta wrote:
> Hi Vlad,
>
> Thanks a lot for the comments. I have incorporated all of them in the
> updated patch below.
One think I forgot to mention the first time, and just thought of it,
is that since you are introducing a new sysctl, it would be very good
to document it in Documents/networking/ip-sysctl.txt.
There is an SCTP section with all current sctp parameters documented.
Thanks
-vlad
>
> Regards,
> Bhaskar
>
>
> Patch Summary:
> =============
> 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 iptables prerouting
> chains convert destination 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 (same IP address with
> different vlan id) a Layer-5 application listens on link local IP's,
> and there is a DNAT rule that maps the destination 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 in init/init-ack
> 3 - Enable address scoping but allow IPv4 link local address in init/init-ack
>
> Patch generated against kernel 2.6.31-rc7.
>
>
> Signed-off-by: Bhaskar Dutta <bhaskar.dutta@xxxxxxxxxxxxxxx>
> ---
> Documentation/networking/ip-sysctl.txt | 10 ++++++++++
> include/net/sctp/constants.h | 7 +++++++
> include/net/sctp/structs.h | 10 ++++++++++
> net/sctp/bind_addr.c | 21 ++++++++++++++++++++-
> net/sctp/protocol.c | 11 ++++++-----
> net/sctp/sysctl.c | 12 ++++++++++++
> 6 files changed, 65 insertions(+), 6 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/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..de46ac6 100644
> --- a/include/net/sctp/structs.h
> +++ b/include/net/sctp/structs.h
> @@ -219,6 +219,15 @@ 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 +261,7 @@ 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/net/sctp/bind_addr.c b/net/sctp/bind_addr.c
> index 6d5944a..7e33508 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
> */
> - if (addr_scope <= scope)
> + 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..ab7151d 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 = CTL_UNNUMBERED,
> + .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 }
> };
>
> --
> 1.6.2.6
> --
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