Re: [PATCH 1/1] sctp: Sysctl configuration for IPv4 Address Scoping

[Vlad Yasevich <vladislav.yasevich@hp.com>]

Bhaskar Dutta wrote:
> On Thu, Sep 3, 2009 at 7:13 PM, Vlad Yasevich<vladislav.yasevich@hp.com> wrote:
>> 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
>>
> 
> It is already there. I'd added the new param at the end of the sctp section.

NM.  must have looked right past it.... ;)

I'll apply.

Thanks
-vlad

>>>>> Documentation/networking/ip-sysctl.txt |   10 ++++++++++
> 
> Thanks,
> Bhaskar
> 
> 
> 
>>> 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@globallogic.com>
>>> ---
>>>  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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>>
>