From 2320bcdae62887555701ea78a46b640ff6b63868 Mon Sep 17 00:00:00 2001 From: Tuong Lien Date: Wed, 24 Jul 2019 08:56:12 +0700 Subject: tipc: fix changeover issues due to large packet In conjunction with changing the interfaces' MTU (e.g. especially in the case of a bonding) where the TIPC links are brought up and down in a short time, a couple of issues were detected with the current link changeover mechanism: 1) When one link is up but immediately forced down again, the failover procedure will be carried out in order to failover all the messages in the link's transmq queue onto the other working link. The link and node state is also set to FAILINGOVER as part of the process. The message will be transmited in form of a FAILOVER_MSG, so its size is plus of 40 bytes (= the message header size). There is no problem if the original message size is not larger than the link's MTU - 40, and indeed this is the max size of a normal payload messages. However, in the situation above, because the link has just been up, the messages in the link's transmq are almost SYNCH_MSGs which had been generated by the link synching procedure, then their size might reach the max value already! When the FAILOVER_MSG is built on the top of such a SYNCH_MSG, its size will exceed the link's MTU. As a result, the messages are dropped silently and the failover procedure will never end up, the link will not be able to exit the FAILINGOVER state, so cannot be re-established. 2) The same scenario above can happen more easily in case the MTU of the links is set differently or when changing. In that case, as long as a large message in the failure link's transmq queue was built and fragmented with its link's MTU > the other link's one, the issue will happen (there is no need of a link synching in advance). 3) The link synching procedure also faces with the same issue but since the link synching is only started upon receipt of a SYNCH_MSG, dropping the message will not result in a state deadlock, but it is not expected as design. The 1) & 3) issues are resolved by the last commit that only a dummy SYNCH_MSG (i.e. without data) is generated at the link synching, so the size of a FAILOVER_MSG if any then will never exceed the link's MTU. For the 2) issue, the only solution is trying to fragment the messages in the failure link's transmq queue according to the working link's MTU so they can be failovered then. A new function is made to accomplish this, it will still be a TUNNEL PROTOCOL/FAILOVER MSG but if the original message size is too large, it will be fragmented & reassembled at the receiving side. Acked-by: Ying Xue Acked-by: Jon Maloy Signed-off-by: Tuong Lien Signed-off-by: David S. Miller --- net/tipc/msg.c | 59 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 59 insertions(+) (limited to 'net/tipc/msg.c') diff --git a/net/tipc/msg.c b/net/tipc/msg.c index f48e5857210f..e6d49cdc61b4 100644 --- a/net/tipc/msg.c +++ b/net/tipc/msg.c @@ -243,6 +243,65 @@ bool tipc_msg_validate(struct sk_buff **_skb) return true; } +/** + * tipc_msg_fragment - build a fragment skb list for TIPC message + * + * @skb: TIPC message skb + * @hdr: internal msg header to be put on the top of the fragments + * @pktmax: max size of a fragment incl. the header + * @frags: returned fragment skb list + * + * Returns 0 if the fragmentation is successful, otherwise: -EINVAL + * or -ENOMEM + */ +int tipc_msg_fragment(struct sk_buff *skb, const struct tipc_msg *hdr, + int pktmax, struct sk_buff_head *frags) +{ + int pktno, nof_fragms, dsz, dmax, eat; + struct tipc_msg *_hdr; + struct sk_buff *_skb; + u8 *data; + + /* Non-linear buffer? */ + if (skb_linearize(skb)) + return -ENOMEM; + + data = (u8 *)skb->data; + dsz = msg_size(buf_msg(skb)); + dmax = pktmax - INT_H_SIZE; + if (dsz <= dmax || !dmax) + return -EINVAL; + + nof_fragms = dsz / dmax + 1; + for (pktno = 1; pktno <= nof_fragms; pktno++) { + if (pktno < nof_fragms) + eat = dmax; + else + eat = dsz % dmax; + /* Allocate a new fragment */ + _skb = tipc_buf_acquire(INT_H_SIZE + eat, GFP_ATOMIC); + if (!_skb) + goto error; + skb_orphan(_skb); + __skb_queue_tail(frags, _skb); + /* Copy header & data to the fragment */ + skb_copy_to_linear_data(_skb, hdr, INT_H_SIZE); + skb_copy_to_linear_data_offset(_skb, INT_H_SIZE, data, eat); + data += eat; + /* Update the fragment's header */ + _hdr = buf_msg(_skb); + msg_set_fragm_no(_hdr, pktno); + msg_set_nof_fragms(_hdr, nof_fragms); + msg_set_size(_hdr, INT_H_SIZE + eat); + } + return 0; + +error: + __skb_queue_purge(frags); + __skb_queue_head_init(frags); + return -ENOMEM; +} + /** * tipc_msg_build - create buffer chain containing specified header and data * @mhdr: Message header, to be prepended to data -- cgit v1.2.3-58-ga151