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Date: Thu, 15 Mar 2018 00:12:32 +0800
From: Xin Long <lucien.xin@...il.com>
To: Neil Horman <nhorman@...driver.com>
Cc: network dev <netdev@...r.kernel.org>, linux-sctp@...r.kernel.org,
Marcelo Ricardo Leitner <marcelo.leitner@...il.com>,
davem <davem@...emloft.net>
Subject: Re: [PATCH net-next 1/5] sctp: add refcnt support for sh_key
On Wed, Mar 14, 2018 at 9:59 PM, Neil Horman <nhorman@...driver.com> wrote:
> On Wed, Mar 14, 2018 at 07:05:30PM +0800, Xin Long wrote:
>> With refcnt support for sh_key, chunks auth sh_keys can be decided
>> before enqueuing it. Changing the active key later will not affect
>> the chunks already enqueued.
>>
>> Furthermore, this is necessary when adding the support for authinfo
>> for sendmsg in next patch.
>>
>> Note that struct sctp_chunk can't be grown due to that performance
>> drop issue on slow cpu, so it just reuses head_skb memory for shkey
>> in sctp_chunk.
>>
>> Signed-off-by: Xin Long <lucien.xin@...il.com>
>> ---
>> include/net/sctp/auth.h | 9 +++--
>> include/net/sctp/sm.h | 3 +-
>> include/net/sctp/structs.h | 9 +++--
>> net/sctp/auth.c | 86 +++++++++++++++++++++++-----------------------
>> net/sctp/chunk.c | 5 +++
>> net/sctp/output.c | 18 ++++++++--
>> net/sctp/sm_make_chunk.c | 15 ++++++--
>> net/sctp/sm_statefuns.c | 11 +++---
>> net/sctp/socket.c | 6 ++++
>> 9 files changed, 104 insertions(+), 58 deletions(-)
>>
>> diff --git a/include/net/sctp/auth.h b/include/net/sctp/auth.h
>> index e5c57d0..017c1aa 100644
>> --- a/include/net/sctp/auth.h
>> +++ b/include/net/sctp/auth.h
>> @@ -62,8 +62,9 @@ struct sctp_auth_bytes {
>> /* Definition for a shared key, weather endpoint or association */
>> struct sctp_shared_key {
>> struct list_head key_list;
>> - __u16 key_id;
>> struct sctp_auth_bytes *key;
>> + refcount_t refcnt;
>> + __u16 key_id;
>> };
>>
>> #define key_for_each(__key, __list_head) \
>> @@ -103,8 +104,10 @@ int sctp_auth_send_cid(enum sctp_cid chunk,
>> int sctp_auth_recv_cid(enum sctp_cid chunk,
>> const struct sctp_association *asoc);
>> void sctp_auth_calculate_hmac(const struct sctp_association *asoc,
>> - struct sk_buff *skb,
>> - struct sctp_auth_chunk *auth, gfp_t gfp);
>> + struct sk_buff *skb, struct sctp_auth_chunk *auth,
>> + struct sctp_shared_key *ep_key, gfp_t gfp);
>> +void sctp_auth_shkey_release(struct sctp_shared_key *sh_key);
>> +void sctp_auth_shkey_hold(struct sctp_shared_key *sh_key);
>>
>> /* API Helpers */
>> int sctp_auth_ep_add_chunkid(struct sctp_endpoint *ep, __u8 chunk_id);
>> diff --git a/include/net/sctp/sm.h b/include/net/sctp/sm.h
>> index 2883c43..2d0e782 100644
>> --- a/include/net/sctp/sm.h
>> +++ b/include/net/sctp/sm.h
>> @@ -263,7 +263,8 @@ int sctp_process_asconf_ack(struct sctp_association *asoc,
>> struct sctp_chunk *sctp_make_fwdtsn(const struct sctp_association *asoc,
>> __u32 new_cum_tsn, size_t nstreams,
>> struct sctp_fwdtsn_skip *skiplist);
>> -struct sctp_chunk *sctp_make_auth(const struct sctp_association *asoc);
>> +struct sctp_chunk *sctp_make_auth(const struct sctp_association *asoc,
>> + __u16 key_id);
>> struct sctp_chunk *sctp_make_strreset_req(const struct sctp_association *asoc,
>> __u16 stream_num, __be16 *stream_list,
>> bool out, bool in);
>> diff --git a/include/net/sctp/structs.h b/include/net/sctp/structs.h
>> index ec6e46b..49ad67b 100644
>> --- a/include/net/sctp/structs.h
>> +++ b/include/net/sctp/structs.h
>> @@ -577,8 +577,12 @@ struct sctp_chunk {
>> /* This points to the sk_buff containing the actual data. */
>> struct sk_buff *skb;
>>
>> - /* In case of GSO packets, this will store the head one */
>> - struct sk_buff *head_skb;
>> + union {
>> + /* In case of GSO packets, this will store the head one */
>> + struct sk_buff *head_skb;
>> + /* In case of auth enabled, this will point to the shkey */
>> + struct sctp_shared_key *shkey;
>> + };
> Why do you need to add this at all? You add the shared key pointer to the
> association in this patch, and sctp_chunk already has a pointer to the
> association, so you should already be able to find the shared key via
> chunk->asoc->shkey, no?
We need this, because one asoc can have a list of shared keys.
When sending a msg, we can even choose one of these keys with
cmsg info (cmsgs->authinfo) for this msg, which is that
5.3.8. SCTP AUTH Information Structure (SCTP_AUTHINFO)
is supposed to do. (Patch 2/5)
After this patchset, asoc->shkey (or we can say active shkey) is
more like default shkey. It will be used only when SCTP_AUTHINFO
is not set in cmsg info.
>
>
>>
>> /* These are the SCTP headers by reverse order in a packet.
>> * Note that some of these may happen more than once. In that
>> @@ -1995,6 +1999,7 @@ struct sctp_association {
>> * The current generated assocaition shared key (secret)
>> */
>> struct sctp_auth_bytes *asoc_shared_key;
>> + struct sctp_shared_key *shkey;
>>
>> /* SCTP AUTH: hmac id of the first peer requested algorithm
>> * that we support.
>> diff --git a/net/sctp/auth.c b/net/sctp/auth.c
>> index 00667c5..e5214fd 100644
>> --- a/net/sctp/auth.c
>> +++ b/net/sctp/auth.c
>> @@ -101,13 +101,14 @@ struct sctp_shared_key *sctp_auth_shkey_create(__u16 key_id, gfp_t gfp)
>> return NULL;
>>
>> INIT_LIST_HEAD(&new->key_list);
>> + refcount_set(&new->refcnt, 1);
>> new->key_id = key_id;
>>
>> return new;
>> }
>>
>> /* Free the shared key structure */
>> -static void sctp_auth_shkey_free(struct sctp_shared_key *sh_key)
>> +static void sctp_auth_shkey_destroy(struct sctp_shared_key *sh_key)
>> {
>> BUG_ON(!list_empty(&sh_key->key_list));
>> sctp_auth_key_put(sh_key->key);
>> @@ -115,6 +116,17 @@ static void sctp_auth_shkey_free(struct sctp_shared_key *sh_key)
>> kfree(sh_key);
>> }
>>
>> +void sctp_auth_shkey_release(struct sctp_shared_key *sh_key)
>> +{
>> + if (refcount_dec_and_test(&sh_key->refcnt))
>> + sctp_auth_shkey_destroy(sh_key);
>> +}
>> +
>> +void sctp_auth_shkey_hold(struct sctp_shared_key *sh_key)
>> +{
>> + refcount_inc(&sh_key->refcnt);
>> +}
>> +
>> /* Destroy the entire key list. This is done during the
>> * associon and endpoint free process.
>> */
>> @@ -128,7 +140,7 @@ void sctp_auth_destroy_keys(struct list_head *keys)
>>
>> key_for_each_safe(ep_key, tmp, keys) {
>> list_del_init(&ep_key->key_list);
>> - sctp_auth_shkey_free(ep_key);
>> + sctp_auth_shkey_release(ep_key);
>> }
>> }
>>
>> @@ -409,13 +421,19 @@ int sctp_auth_asoc_init_active_key(struct sctp_association *asoc, gfp_t gfp)
>>
>> sctp_auth_key_put(asoc->asoc_shared_key);
>> asoc->asoc_shared_key = secret;
>> + asoc->shkey = ep_key;
>>
>> /* Update send queue in case any chunk already in there now
>> * needs authenticating
>> */
>> list_for_each_entry(chunk, &asoc->outqueue.out_chunk_list, list) {
>> - if (sctp_auth_send_cid(chunk->chunk_hdr->type, asoc))
>> + if (sctp_auth_send_cid(chunk->chunk_hdr->type, asoc)) {
>> chunk->auth = 1;
>> + if (!chunk->shkey) {
>> + chunk->shkey = asoc->shkey;
>> + sctp_auth_shkey_hold(chunk->shkey);
>> + }
>> + }
> Do we really need to take a reference for every chunk we send? Wouldn't it be
> sufficient to just hold the shared key until the association is released?
As we can use other shkey(not only asoc->shkey) for one chunk, and even
different shkeys for different chunks, we have to hold it in case that this
shkey may be removed/freed when this chunk is still queuing up in
outqueue, until this chunk has been transmitted and freed.
make sense?
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