mctp: Implement message fragmentation & reassembly
This change implements MCTP fragmentation (based on route & device MTU), and corresponding reassembly. The MCTP specification only allows for fragmentation on the originating message endpoint, and reassembly on the destination endpoint - intermediate nodes do not need to reassemble/refragment. Consequently, we only fragment in the local transmit path, and reassemble locally-bound packets. Messages are required to be in-order, so we simply cancel reassembly on out-of-order or missing packets. In the fragmentation path, we just break up the message into MTU-sized fragments; the skb structure is a simple copy for now, which we can later improve with a shared data implementation. For reassembly, we keep track of incoming message fragments using the existing tag infrastructure, allocating a key on the (src,dest,tag) tuple, and reassembles matching fragments into a skb->frag_list. Signed-off-by: Jeremy Kerr <jk@codeconstruct.com.au> Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Jeremy Kerr
David S. Miller
Родитель
833ef3b91d
Коммит
4a992bbd36
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@ -84,9 +84,21 @@ struct mctp_sock {
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* updates to either list are performed under the netns_mctp->keys
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* lock.
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*
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* - there is a single destruction path for a mctp_sk_key - through socket
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* unhash (see mctp_sk_unhash). This performs the list removal under
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* keys_lock.
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* - a key may have a sk_buff attached as part of an in-progress message
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* reassembly (->reasm_head). The reassembly context is protected by
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* reasm_lock, which may be acquired with the keys lock (above) held, if
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* necessary. Consequently, keys lock *cannot* be acquired with the
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* reasm_lock held.
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*
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* - there are two destruction paths for a mctp_sk_key:
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*
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* - through socket unhash (see mctp_sk_unhash). This performs the list
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* removal under keys_lock.
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*
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* - where a key is established to receive a reply message: after receiving
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* the (complete) reply, or during reassembly errors. Here, we clean up
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* the reassembly context (marking reasm_dead, to prevent another from
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* starting), and remove the socket from the netns & socket lists.
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*/
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struct mctp_sk_key {
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mctp_eid_t peer_addr;
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@ -102,6 +114,13 @@ struct mctp_sk_key {
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/* per-socket list */
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struct hlist_node sklist;
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/* incoming fragment reassembly context */
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spinlock_t reasm_lock;
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struct sk_buff *reasm_head;
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struct sk_buff **reasm_tailp;
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bool reasm_dead;
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u8 last_seq;
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struct rcu_head rcu;
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};
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@ -263,6 +263,14 @@ static void mctp_sk_unhash(struct sock *sk)
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hlist_for_each_entry_safe(key, tmp, &msk->keys, sklist) {
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hlist_del_rcu(&key->sklist);
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hlist_del_rcu(&key->hlist);
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spin_lock(&key->reasm_lock);
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if (key->reasm_head)
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kfree_skb(key->reasm_head);
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key->reasm_head = NULL;
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key->reasm_dead = true;
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spin_unlock(&key->reasm_lock);
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kfree_rcu(key, rcu);
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}
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spin_unlock_irqrestore(&net->mctp.keys_lock, flags);
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376
net/mctp/route.c
376
net/mctp/route.c
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@ -23,6 +23,8 @@
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#include <net/netlink.h>
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#include <net/sock.h>
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static const unsigned int mctp_message_maxlen = 64 * 1024;
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/* route output callbacks */
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static int mctp_route_discard(struct mctp_route *route, struct sk_buff *skb)
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{
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@ -105,14 +107,125 @@ static struct mctp_sk_key *mctp_lookup_key(struct net *net, struct sk_buff *skb,
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return ret;
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}
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static struct mctp_sk_key *mctp_key_alloc(struct mctp_sock *msk,
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mctp_eid_t local, mctp_eid_t peer,
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u8 tag, gfp_t gfp)
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{
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struct mctp_sk_key *key;
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key = kzalloc(sizeof(*key), gfp);
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if (!key)
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return NULL;
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key->peer_addr = peer;
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key->local_addr = local;
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key->tag = tag;
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key->sk = &msk->sk;
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spin_lock_init(&key->reasm_lock);
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return key;
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}
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static int mctp_key_add(struct mctp_sk_key *key, struct mctp_sock *msk)
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{
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struct net *net = sock_net(&msk->sk);
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struct mctp_sk_key *tmp;
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unsigned long flags;
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int rc = 0;
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spin_lock_irqsave(&net->mctp.keys_lock, flags);
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hlist_for_each_entry(tmp, &net->mctp.keys, hlist) {
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if (mctp_key_match(tmp, key->local_addr, key->peer_addr,
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key->tag)) {
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rc = -EEXIST;
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break;
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}
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}
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if (!rc) {
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hlist_add_head(&key->hlist, &net->mctp.keys);
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hlist_add_head(&key->sklist, &msk->keys);
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}
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spin_unlock_irqrestore(&net->mctp.keys_lock, flags);
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return rc;
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}
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/* Must be called with key->reasm_lock, which it will release. Will schedule
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* the key for an RCU free.
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*/
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static void __mctp_key_unlock_drop(struct mctp_sk_key *key, struct net *net,
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unsigned long flags)
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__releases(&key->reasm_lock)
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{
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struct sk_buff *skb;
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skb = key->reasm_head;
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key->reasm_head = NULL;
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key->reasm_dead = true;
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spin_unlock_irqrestore(&key->reasm_lock, flags);
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spin_lock_irqsave(&net->mctp.keys_lock, flags);
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hlist_del_rcu(&key->hlist);
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hlist_del_rcu(&key->sklist);
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spin_unlock_irqrestore(&net->mctp.keys_lock, flags);
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kfree_rcu(key, rcu);
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if (skb)
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kfree_skb(skb);
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}
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static int mctp_frag_queue(struct mctp_sk_key *key, struct sk_buff *skb)
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{
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struct mctp_hdr *hdr = mctp_hdr(skb);
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u8 exp_seq, this_seq;
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this_seq = (hdr->flags_seq_tag >> MCTP_HDR_SEQ_SHIFT)
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& MCTP_HDR_SEQ_MASK;
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if (!key->reasm_head) {
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key->reasm_head = skb;
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key->reasm_tailp = &(skb_shinfo(skb)->frag_list);
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key->last_seq = this_seq;
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return 0;
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}
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exp_seq = (key->last_seq + 1) & MCTP_HDR_SEQ_MASK;
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if (this_seq != exp_seq)
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return -EINVAL;
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if (key->reasm_head->len + skb->len > mctp_message_maxlen)
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return -EINVAL;
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skb->next = NULL;
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skb->sk = NULL;
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*key->reasm_tailp = skb;
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key->reasm_tailp = &skb->next;
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key->last_seq = this_seq;
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key->reasm_head->data_len += skb->len;
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key->reasm_head->len += skb->len;
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key->reasm_head->truesize += skb->truesize;
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return 0;
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}
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static int mctp_route_input(struct mctp_route *route, struct sk_buff *skb)
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{
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struct net *net = dev_net(skb->dev);
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struct mctp_sk_key *key;
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struct mctp_sock *msk;
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struct mctp_hdr *mh;
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unsigned long f;
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u8 tag, flags;
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int rc;
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msk = NULL;
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rc = -EINVAL;
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/* we may be receiving a locally-routed packet; drop source sk
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* accounting
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@ -121,50 +234,144 @@ static int mctp_route_input(struct mctp_route *route, struct sk_buff *skb)
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/* ensure we have enough data for a header and a type */
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if (skb->len < sizeof(struct mctp_hdr) + 1)
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goto drop;
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goto out;
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/* grab header, advance data ptr */
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mh = mctp_hdr(skb);
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skb_pull(skb, sizeof(struct mctp_hdr));
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if (mh->ver != 1)
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goto drop;
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goto out;
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/* TODO: reassembly */
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if ((mh->flags_seq_tag & (MCTP_HDR_FLAG_SOM | MCTP_HDR_FLAG_EOM))
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!= (MCTP_HDR_FLAG_SOM | MCTP_HDR_FLAG_EOM))
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goto drop;
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flags = mh->flags_seq_tag & (MCTP_HDR_FLAG_SOM | MCTP_HDR_FLAG_EOM);
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tag = mh->flags_seq_tag & (MCTP_HDR_TAG_MASK | MCTP_HDR_FLAG_TO);
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rcu_read_lock();
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/* 1. lookup socket matching (src,dest,tag) */
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/* lookup socket / reasm context, exactly matching (src,dest,tag) */
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key = mctp_lookup_key(net, skb, mh->src);
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/* 2. lookup socket macthing (BCAST,dest,tag) */
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if (!key)
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key = mctp_lookup_key(net, skb, MCTP_ADDR_ANY);
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if (flags & MCTP_HDR_FLAG_SOM) {
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if (key) {
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msk = container_of(key->sk, struct mctp_sock, sk);
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} else {
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/* first response to a broadcast? do a more general
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* key lookup to find the socket, but don't use this
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* key for reassembly - we'll create a more specific
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* one for future packets if required (ie, !EOM).
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*/
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key = mctp_lookup_key(net, skb, MCTP_ADDR_ANY);
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if (key) {
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msk = container_of(key->sk,
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struct mctp_sock, sk);
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key = NULL;
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}
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}
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/* 3. SOM? -> lookup bound socket, conditionally (!EOM) create
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* mapping for future (1)/(2).
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*/
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if (key)
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msk = container_of(key->sk, struct mctp_sock, sk);
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else if (!msk && (mh->flags_seq_tag & MCTP_HDR_FLAG_SOM))
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msk = mctp_lookup_bind(net, skb);
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if (!key && !msk && (tag & MCTP_HDR_FLAG_TO))
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msk = mctp_lookup_bind(net, skb);
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if (!msk)
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goto unlock_drop;
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if (!msk) {
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rc = -ENOENT;
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goto out_unlock;
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}
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sock_queue_rcv_skb(&msk->sk, skb);
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/* single-packet message? deliver to socket, clean up any
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* pending key.
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*/
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if (flags & MCTP_HDR_FLAG_EOM) {
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sock_queue_rcv_skb(&msk->sk, skb);
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if (key) {
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spin_lock_irqsave(&key->reasm_lock, f);
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/* we've hit a pending reassembly; not much we
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* can do but drop it
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*/
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__mctp_key_unlock_drop(key, net, f);
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}
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rc = 0;
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goto out_unlock;
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}
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/* broadcast response or a bind() - create a key for further
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* packets for this message
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*/
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if (!key) {
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key = mctp_key_alloc(msk, mh->dest, mh->src,
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tag, GFP_ATOMIC);
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if (!key) {
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rc = -ENOMEM;
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goto out_unlock;
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}
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/* we can queue without the reasm lock here, as the
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* key isn't observable yet
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*/
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mctp_frag_queue(key, skb);
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/* if the key_add fails, we've raced with another
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* SOM packet with the same src, dest and tag. There's
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* no way to distinguish future packets, so all we
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* can do is drop; we'll free the skb on exit from
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* this function.
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*/
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rc = mctp_key_add(key, msk);
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if (rc)
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kfree(key);
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} else {
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/* existing key: start reassembly */
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spin_lock_irqsave(&key->reasm_lock, f);
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if (key->reasm_head || key->reasm_dead) {
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/* duplicate start? drop everything */
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__mctp_key_unlock_drop(key, net, f);
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rc = -EEXIST;
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} else {
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rc = mctp_frag_queue(key, skb);
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spin_unlock_irqrestore(&key->reasm_lock, f);
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}
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}
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} else if (key) {
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/* this packet continues a previous message; reassemble
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* using the message-specific key
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*/
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spin_lock_irqsave(&key->reasm_lock, f);
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/* we need to be continuing an existing reassembly... */
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if (!key->reasm_head)
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rc = -EINVAL;
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else
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rc = mctp_frag_queue(key, skb);
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/* end of message? deliver to socket, and we're done with
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* the reassembly/response key
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*/
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if (!rc && flags & MCTP_HDR_FLAG_EOM) {
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sock_queue_rcv_skb(key->sk, key->reasm_head);
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key->reasm_head = NULL;
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__mctp_key_unlock_drop(key, net, f);
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} else {
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spin_unlock_irqrestore(&key->reasm_lock, f);
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}
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} else {
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/* not a start, no matching key */
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rc = -ENOENT;
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}
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out_unlock:
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rcu_read_unlock();
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out:
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if (rc)
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kfree_skb(skb);
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return rc;
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}
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return 0;
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unlock_drop:
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rcu_read_unlock();
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drop:
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kfree_skb(skb);
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return 0;
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static unsigned int mctp_route_mtu(struct mctp_route *rt)
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{
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return rt->mtu ?: READ_ONCE(rt->dev->dev->mtu);
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}
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static int mctp_route_output(struct mctp_route *route, struct sk_buff *skb)
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@ -228,8 +435,6 @@ static void mctp_reserve_tag(struct net *net, struct mctp_sk_key *key,
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lockdep_assert_held(&mns->keys_lock);
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key->sk = &msk->sk;
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/* we hold the net->key_lock here, allowing updates to both
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* then net and sk
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*/
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@ -251,11 +456,9 @@ static int mctp_alloc_local_tag(struct mctp_sock *msk,
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u8 tagbits;
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/* be optimistic, alloc now */
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key = kzalloc(sizeof(*key), GFP_KERNEL);
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key = mctp_key_alloc(msk, saddr, daddr, 0, GFP_KERNEL);
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if (!key)
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return -ENOMEM;
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key->local_addr = saddr;
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key->peer_addr = daddr;
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/* 8 possible tag values */
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tagbits = 0xff;
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|
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@ -340,6 +543,86 @@ int mctp_do_route(struct mctp_route *rt, struct sk_buff *skb)
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return rc;
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}
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static int mctp_do_fragment_route(struct mctp_route *rt, struct sk_buff *skb,
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unsigned int mtu, u8 tag)
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{
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const unsigned int hlen = sizeof(struct mctp_hdr);
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struct mctp_hdr *hdr, *hdr2;
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unsigned int pos, size;
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struct sk_buff *skb2;
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int rc;
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u8 seq;
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|
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hdr = mctp_hdr(skb);
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seq = 0;
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rc = 0;
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|
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if (mtu < hlen + 1) {
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kfree_skb(skb);
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return -EMSGSIZE;
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}
|
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|
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/* we've got the header */
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skb_pull(skb, hlen);
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|
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for (pos = 0; pos < skb->len;) {
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/* size of message payload */
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size = min(mtu - hlen, skb->len - pos);
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|
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skb2 = alloc_skb(MCTP_HEADER_MAXLEN + hlen + size, GFP_KERNEL);
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if (!skb2) {
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rc = -ENOMEM;
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break;
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}
|
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/* generic skb copy */
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skb2->protocol = skb->protocol;
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skb2->priority = skb->priority;
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skb2->dev = skb->dev;
|
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memcpy(skb2->cb, skb->cb, sizeof(skb2->cb));
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|
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if (skb->sk)
|
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skb_set_owner_w(skb2, skb->sk);
|
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|
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/* establish packet */
|
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skb_reserve(skb2, MCTP_HEADER_MAXLEN);
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skb_reset_network_header(skb2);
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skb_put(skb2, hlen + size);
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skb2->transport_header = skb2->network_header + hlen;
|
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|
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/* copy header fields, calculate SOM/EOM flags & seq */
|
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hdr2 = mctp_hdr(skb2);
|
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hdr2->ver = hdr->ver;
|
||||
hdr2->dest = hdr->dest;
|
||||
hdr2->src = hdr->src;
|
||||
hdr2->flags_seq_tag = tag &
|
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(MCTP_HDR_TAG_MASK | MCTP_HDR_FLAG_TO);
|
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|
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if (pos == 0)
|
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hdr2->flags_seq_tag |= MCTP_HDR_FLAG_SOM;
|
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|
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if (pos + size == skb->len)
|
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hdr2->flags_seq_tag |= MCTP_HDR_FLAG_EOM;
|
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|
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hdr2->flags_seq_tag |= seq << MCTP_HDR_SEQ_SHIFT;
|
||||
|
||||
/* copy message payload */
|
||||
skb_copy_bits(skb, pos, skb_transport_header(skb2), size);
|
||||
|
||||
/* do route, but don't drop the rt reference */
|
||||
rc = rt->output(rt, skb2);
|
||||
if (rc)
|
||||
break;
|
||||
|
||||
seq = (seq + 1) & MCTP_HDR_SEQ_MASK;
|
||||
pos += size;
|
||||
}
|
||||
|
||||
mctp_route_release(rt);
|
||||
consume_skb(skb);
|
||||
return rc;
|
||||
}
|
||||
|
||||
int mctp_local_output(struct sock *sk, struct mctp_route *rt,
|
||||
struct sk_buff *skb, mctp_eid_t daddr, u8 req_tag)
|
||||
{
|
||||
|
|
@ -347,6 +630,7 @@ int mctp_local_output(struct sock *sk, struct mctp_route *rt,
|
|||
struct mctp_skb_cb *cb = mctp_cb(skb);
|
||||
struct mctp_hdr *hdr;
|
||||
unsigned long flags;
|
||||
unsigned int mtu;
|
||||
mctp_eid_t saddr;
|
||||
int rc;
|
||||
u8 tag;
|
||||
|
|
@ -376,26 +660,32 @@ int mctp_local_output(struct sock *sk, struct mctp_route *rt,
|
|||
tag = req_tag;
|
||||
}
|
||||
|
||||
/* TODO: we have the route MTU here; packetise */
|
||||
|
||||
skb->protocol = htons(ETH_P_MCTP);
|
||||
skb->priority = 0;
|
||||
skb_reset_transport_header(skb);
|
||||
skb_push(skb, sizeof(struct mctp_hdr));
|
||||
skb_reset_network_header(skb);
|
||||
hdr = mctp_hdr(skb);
|
||||
hdr->ver = 1;
|
||||
hdr->dest = daddr;
|
||||
hdr->src = saddr;
|
||||
hdr->flags_seq_tag = MCTP_HDR_FLAG_SOM | MCTP_HDR_FLAG_EOM | /* TODO */
|
||||
tag;
|
||||
|
||||
skb->dev = rt->dev->dev;
|
||||
skb->protocol = htons(ETH_P_MCTP);
|
||||
skb->priority = 0;
|
||||
|
||||
/* cb->net will have been set on initial ingress */
|
||||
cb->src = saddr;
|
||||
|
||||
return mctp_do_route(rt, skb);
|
||||
/* set up common header fields */
|
||||
hdr = mctp_hdr(skb);
|
||||
hdr->ver = 1;
|
||||
hdr->dest = daddr;
|
||||
hdr->src = saddr;
|
||||
|
||||
mtu = mctp_route_mtu(rt);
|
||||
|
||||
if (skb->len + sizeof(struct mctp_hdr) <= mtu) {
|
||||
hdr->flags_seq_tag = MCTP_HDR_FLAG_SOM | MCTP_HDR_FLAG_EOM |
|
||||
tag;
|
||||
return mctp_do_route(rt, skb);
|
||||
} else {
|
||||
return mctp_do_fragment_route(rt, skb, mtu, tag);
|
||||
}
|
||||
}
|
||||
|
||||
/* route management */
|
||||
|
|
|
|||
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Ссылка в новой задаче