tipc: don't send gap blocks in ACK messages (b7ffa045) · Commits · 戴 / test

In the commit referred to below we eliminated sending of the 'gap' indicator in regular ACK messages, reserving this to explicit NACK ditto. Unfortunately we missed to also eliminate building of the 'gap block' area in ACK messages. This area is meant to report gaps in the received packet sequence following the initial gap, so that lost packets can be retransmitted earlier and received out-of-sequence packets can be released earlier. However, the interpretation of those blocks is dependent on a complete and correct sequence of gaps and acks. Hence, when the initial gap indicator is missing a single gap block will be interpreted as an acknowledgment of all preceding packets. This may lead to packets being released prematurely from the sender's transmit queue, with easily predicatble consequences. We now fix this by not building any gap block area if there is no initial gap to report. Fixes: commit ("tipc: eliminate gap indicator from ACK messages") Signed-off-by:

Jon Maloy <jon.maloy@ericsson.com> Signed-off-by:

David S. Miller <davem@davemloft.net>

net/tipc/link.c

+4 −4

Original line number	Diff line number	Diff line
		@@ -250,7 +250,7 @@ static int tipc_link_build_nack_msg(struct tipc_link *l,
		static void tipc_link_build_bc_init_msg(struct tipc_link *l,
		struct sk_buff_head *xmitq);
		static int tipc_link_release_pkts(struct tipc_link *l, u16 to);
		static u16 tipc_build_gap_ack_blks(struct tipc_link l, void data);
		static u16 tipc_build_gap_ack_blks(struct tipc_link l, void data, u16 gap);
		static int tipc_link_advance_transmq(struct tipc_link *l, u16 acked, u16 gap,
		struct tipc_gap_ack_blks *ga,
		struct sk_buff_head *xmitq);
		@@ -1423,14 +1423,14 @@ static int tipc_link_release_pkts(struct tipc_link *l, u16 acked)
		*
		* returns the actual allocated memory size
		*/
		static u16 tipc_build_gap_ack_blks(struct tipc_link l, void data)
		static u16 tipc_build_gap_ack_blks(struct tipc_link l, void data, u16 gap)
		{
		struct sk_buff *skb = skb_peek(&l->deferdq);
		struct tipc_gap_ack_blks *ga = data;
		u16 len, expect, seqno = 0;
		u8 n = 0;

		if (!skb)
		if (!skb \|\| !gap)
		goto exit;

		expect = buf_seqno(skb);
		@@ -1739,7 +1739,7 @@ static void tipc_link_build_proto_msg(struct tipc_link *l, int mtyp, bool probe,
		msg_set_probe(hdr, probe);
		msg_set_is_keepalive(hdr, probe \|\| probe_reply);
		if (l->peer_caps & TIPC_GAP_ACK_BLOCK)
		glen = tipc_build_gap_ack_blks(l, data);
		glen = tipc_build_gap_ack_blks(l, data, rcvgap);
		tipc_mon_prep(l->net, data + glen, &dlen, mstate, l->bearer_id);
		msg_set_size(hdr, INT_H_SIZE + glen + dlen);
		skb_trim(skb, INT_H_SIZE + glen + dlen);

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