linux/net/tipc/socket.h

90 lines
3.2 KiB

tipc: compensate for double accounting in socket rcv buffer The function net/core/sock.c::__release_sock() runs a tight loop to move buffers from the socket backlog queue to the receive queue. As a security measure, sk_backlog.len of the receiving socket is not set to zero until after the loop is finished, i.e., until the whole backlog queue has been transferred to the receive queue. During this transfer, the data that has already been moved is counted both in the backlog queue and the receive queue, hence giving an incorrect picture of the available queue space for new arriving buffers. This leads to unnecessary rejection of buffers by sk_add_backlog(), which in TIPC leads to unnecessarily broken connections. In this commit, we compensate for this double accounting by adding a counter that keeps track of it. The function socket.c::backlog_rcv() receives buffers one by one from __release_sock(), and adds them to the socket receive queue. If the transfer is successful, it increases a new atomic counter 'tipc_sock::dupl_rcvcnt' with 'truesize' of the transferred buffer. If a new buffer arrives during this transfer and finds the socket busy (owned), we attempt to add it to the backlog. However, when sk_add_backlog() is called, we adjust the 'limit' parameter with the value of the new counter, so that the risk of inadvertent rejection is eliminated. It should be noted that this change does not invalidate the original purpose of zeroing 'sk_backlog.len' after the full transfer. We set an upper limit for dupl_rcvcnt, so that if a 'wild' sender (i.e., one that doesn't respect the send window) keeps pumping in buffers to sk_add_backlog(), he will eventually reach an upper limit, (2 x TIPC_CONN_OVERLOAD_LIMIT). After that, no messages can be added to the backlog, and the connection will be broken. Ordinary, well- behaved senders will never reach this buffer limit at all. Signed-off-by: Jon Maloy <jon.maloy@ericsson.com> Reviewed-by: Ying Xue <ying.xue@windriver.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2014-05-14 05:39:09 -04:00
tipc: simplify connection congestion handling As a consequence of the recently introduced serialized access to the socket in commit 8d94168a761819d10252bab1f8de6d7b202c3baa ("tipc: same receive code path for connection protocol and data messages") we can make a number of simplifications in the detection and handling of connection congestion situations. - We don't need to keep two counters, one for sent messages and one for acked messages. There is no longer any risk for races between acknowledge messages arriving in BH and data message sending running in user context. So we merge this into one counter, 'sent_unacked', which is incremented at sending and subtracted from at acknowledge reception. - We don't need to set the 'congested' field in tipc_port to true before we sent the message, and clear it when sending is successful. (As a matter of fact, it was never necessary; the field was set in link_schedule_port() before any wakeup could arrive anyway.) - We keep the conditions for link congestion and connection connection congestion separated. There would otherwise be a risk that an arriving acknowledge message may wake up a user sleeping because of link congestion. - We can simplify reception of acknowledge messages. We also make some cosmetic/structural changes: - We rename the 'congested' field to the more correct 'link_cong´. - We rename 'conn_unacked' to 'rcv_unacked' - We move the above mentioned fields from struct tipc_port to struct tipc_sock. Signed-off-by: Jon Maloy <jon.maloy@ericsson.com> Reviewed-by: Erik Hugne <erik.hugne@ericsson.com> Reviewed-by: Ying Xue <ying.xue@windriver.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2014-06-25 20:41:42 -05:00
tipc: compensate for double accounting in socket rcv buffer The function net/core/sock.c::__release_sock() runs a tight loop to move buffers from the socket backlog queue to the receive queue. As a security measure, sk_backlog.len of the receiving socket is not set to zero until after the loop is finished, i.e., until the whole backlog queue has been transferred to the receive queue. During this transfer, the data that has already been moved is counted both in the backlog queue and the receive queue, hence giving an incorrect picture of the available queue space for new arriving buffers. This leads to unnecessary rejection of buffers by sk_add_backlog(), which in TIPC leads to unnecessarily broken connections. In this commit, we compensate for this double accounting by adding a counter that keeps track of it. The function socket.c::backlog_rcv() receives buffers one by one from __release_sock(), and adds them to the socket receive queue. If the transfer is successful, it increases a new atomic counter 'tipc_sock::dupl_rcvcnt' with 'truesize' of the transferred buffer. If a new buffer arrives during this transfer and finds the socket busy (owned), we attempt to add it to the backlog. However, when sk_add_backlog() is called, we adjust the 'limit' parameter with the value of the new counter, so that the risk of inadvertent rejection is eliminated. It should be noted that this change does not invalidate the original purpose of zeroing 'sk_backlog.len' after the full transfer. We set an upper limit for dupl_rcvcnt, so that if a 'wild' sender (i.e., one that doesn't respect the send window) keeps pumping in buffers to sk_add_backlog(), he will eventually reach an upper limit, (2 x TIPC_CONN_OVERLOAD_LIMIT). After that, no messages can be added to the backlog, and the connection will be broken. Ordinary, well- behaved senders will never reach this buffer limit at all. Signed-off-by: Jon Maloy <jon.maloy@ericsson.com> Reviewed-by: Ying Xue <ying.xue@windriver.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2014-05-14 05:39:09 -04:00
tipc: simplify connection congestion handling As a consequence of the recently introduced serialized access to the socket in commit 8d94168a761819d10252bab1f8de6d7b202c3baa ("tipc: same receive code path for connection protocol and data messages") we can make a number of simplifications in the detection and handling of connection congestion situations. - We don't need to keep two counters, one for sent messages and one for acked messages. There is no longer any risk for races between acknowledge messages arriving in BH and data message sending running in user context. So we merge this into one counter, 'sent_unacked', which is incremented at sending and subtracted from at acknowledge reception. - We don't need to set the 'congested' field in tipc_port to true before we sent the message, and clear it when sending is successful. (As a matter of fact, it was never necessary; the field was set in link_schedule_port() before any wakeup could arrive anyway.) - We keep the conditions for link congestion and connection connection congestion separated. There would otherwise be a risk that an arriving acknowledge message may wake up a user sleeping because of link congestion. - We can simplify reception of acknowledge messages. We also make some cosmetic/structural changes: - We rename the 'congested' field to the more correct 'link_cong´. - We rename 'conn_unacked' to 'rcv_unacked' - We move the above mentioned fields from struct tipc_port to struct tipc_sock. Signed-off-by: Jon Maloy <jon.maloy@ericsson.com> Reviewed-by: Erik Hugne <erik.hugne@ericsson.com> Reviewed-by: Ying Xue <ying.xue@windriver.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2014-06-25 20:41:42 -05:00
tipc: simplify connection congestion handling As a consequence of the recently introduced serialized access to the socket in commit 8d94168a761819d10252bab1f8de6d7b202c3baa ("tipc: same receive code path for connection protocol and data messages") we can make a number of simplifications in the detection and handling of connection congestion situations. - We don't need to keep two counters, one for sent messages and one for acked messages. There is no longer any risk for races between acknowledge messages arriving in BH and data message sending running in user context. So we merge this into one counter, 'sent_unacked', which is incremented at sending and subtracted from at acknowledge reception. - We don't need to set the 'congested' field in tipc_port to true before we sent the message, and clear it when sending is successful. (As a matter of fact, it was never necessary; the field was set in link_schedule_port() before any wakeup could arrive anyway.) - We keep the conditions for link congestion and connection connection congestion separated. There would otherwise be a risk that an arriving acknowledge message may wake up a user sleeping because of link congestion. - We can simplify reception of acknowledge messages. We also make some cosmetic/structural changes: - We rename the 'congested' field to the more correct 'link_cong´. - We rename 'conn_unacked' to 'rcv_unacked' - We move the above mentioned fields from struct tipc_port to struct tipc_sock. Signed-off-by: Jon Maloy <jon.maloy@ericsson.com> Reviewed-by: Erik Hugne <erik.hugne@ericsson.com> Reviewed-by: Ying Xue <ying.xue@windriver.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2014-06-25 20:41:42 -05:00