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

[Bhaskar Dutta <bhaskie@gmail.com>]

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.
>>>> 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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>
>