- 18 5月, 2015 1 次提交
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由 Eric Dumazet 提交于
Introduce an optimized version of sk_under_memory_pressure() for TCP. Our intent is to use it in fast paths. Signed-off-by: NEric Dumazet <edumazet@google.com> Signed-off-by: NDavid S. Miller <davem@davemloft.net>
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- 10 5月, 2015 1 次提交
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由 Eric Dumazet 提交于
With the advent of small rto timers in datacenter TCP, (ip route ... rto_min x), the following can happen : 1) Qdisc is full, transmit fails. TCP sets a timer based on icsk_rto to retry the transmit, without exponential backoff. With low icsk_rto, and lot of sockets, all cpus are servicing timer interrupts like crazy. Intent of the code was to retry with a timer between 200 (TCP_RTO_MIN) and 500ms (TCP_RESOURCE_PROBE_INTERVAL) 2) Receivers can send zero windows if they don't drain their receive queue. TCP sends zero window probes, based on icsk_rto current value, with exponential backoff. With /proc/sys/net/ipv4/tcp_retries2 being 15 (or even smaller in some cases), sender can abort in less than one or two minutes ! If receiver stops the sender, it obviously doesn't care of very tight rto. Probability of dropping the ACK reopening the window is not worth the risk. Lets change the base timer to be at least 200ms (TCP_RTO_MIN) for these events (but not normal RTO based retransmits) A followup patch adds a new SNMP counter, as it would have helped a lot diagnosing this issue. Signed-off-by: NEric Dumazet <edumazet@google.com> Signed-off-by: NYuchung Cheng <ycheng@google.com> Acked-by: NNeal Cardwell <ncardwell@google.com> Signed-off-by: NDavid S. Miller <davem@davemloft.net>
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- 06 5月, 2015 1 次提交
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由 Eric Dumazet 提交于
This patch allows a server application to get the TCP SYN headers for its passive connections. This is useful if the server is doing fingerprinting of clients based on SYN packet contents. Two socket options are added: TCP_SAVE_SYN and TCP_SAVED_SYN. The first is used on a socket to enable saving the SYN headers for child connections. This can be set before or after the listen() call. The latter is used to retrieve the SYN headers for passive connections, if the parent listener has enabled TCP_SAVE_SYN. TCP_SAVED_SYN is read once, it frees the saved SYN headers. The data returned in TCP_SAVED_SYN are network (IPv4/IPv6) and TCP headers. Original patch was written by Tom Herbert, I changed it to not hold a full skb (and associated dst and conntracking reference). We have used such patch for about 3 years at Google. Signed-off-by: NEric Dumazet <edumazet@google.com> Acked-by: NNeal Cardwell <ncardwell@google.com> Tested-by: NNeal Cardwell <ncardwell@google.com> Signed-off-by: NDavid S. Miller <davem@davemloft.net>
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- 04 5月, 2015 3 次提交
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由 Kenneth Klette Jonassen 提交于
Invoking pkts_acked is currently conditioned on FLAG_ACKED: receiving a cumulative ACK of new data, or ACK with SYN flag set. Remove this condition so that CC may get RTT measurements from all SACKs. Cc: Yuchung Cheng <ycheng@google.com> Cc: Eric Dumazet <edumazet@google.com> Cc: Neal Cardwell <ncardwell@google.com> Signed-off-by: NKenneth Klette Jonassen <kennetkl@ifi.uio.no> Signed-off-by: NDavid S. Miller <davem@davemloft.net>
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由 Kenneth Klette Jonassen 提交于
tcp_sacktag_one() always picks the earliest sequence SACKed for RTT. This might not make sense for congestion control in cases where: 1. ACKs are lost, i.e. a SACK following a lost SACK covers both new and old segments at the receiver. 2. The receiver disregards the RFC 5681 recommendation to immediately ACK out-of-order segments. Give congestion control a RTT for the latest segment SACKed, which is the most accurate RTT estimate, but preserve the conservative RTT for RTO. Removes the call to skb_mstamp_get() in tcp_sacktag_one(). Cc: Yuchung Cheng <ycheng@google.com> Cc: Eric Dumazet <edumazet@google.com> Signed-off-by: NKenneth Klette Jonassen <kennetkl@ifi.uio.no> Acked-by: NYuchung Cheng <ycheng@google.com> Signed-off-by: NDavid S. Miller <davem@davemloft.net>
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由 Kenneth Klette Jonassen 提交于
Later patch passes two values set in tcp_sacktag_one() to tcp_clean_rtx_queue(). Prepare passing them via struct tcp_sacktag_state. Acked-by: NYuchung Cheng <ycheng@google.com> Cc: Eric Dumazet <edumazet@google.com> Signed-off-by: NKenneth Klette Jonassen <kennetkl@ifi.uio.no> Signed-off-by: NDavid S. Miller <davem@davemloft.net>
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- 30 4月, 2015 3 次提交
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由 Yuchung Cheng 提交于
tcp_mark_lost_retrans is not used when FACK is disabled. Since tcp_update_reordering may disable FACK, it should be called first before tcp_mark_lost_retrans. Signed-off-by: NYuchung Cheng <ycheng@google.com> Signed-off-by: NNandita Dukkipati <nanditad@google.com> Signed-off-by: NNeal Cardwell <ncardwell@google.com> Signed-off-by: NDavid S. Miller <davem@davemloft.net>
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由 Eric Dumazet 提交于
This patch tracks total number of payload bytes received on a TCP socket. This is the sum of all changes done to tp->rcv_nxt RFC4898 named this : tcpEStatsAppHCThruOctetsReceived This is a 64bit field, and can be fetched both from TCP_INFO getsockopt() if one has a handle on a TCP socket, or from inet_diag netlink facility (iproute2/ss patch will follow) Note that tp->bytes_received was placed near tp->rcv_nxt for best data locality and minimal performance impact. Signed-off-by: NEric Dumazet <edumazet@google.com> Cc: Yuchung Cheng <ycheng@google.com> Cc: Matt Mathis <mattmathis@google.com> Cc: Eric Salo <salo@google.com> Cc: Martin Lau <kafai@fb.com> Cc: Chris Rapier <rapier@psc.edu> Acked-by: NYuchung Cheng <ycheng@google.com> Signed-off-by: NDavid S. Miller <davem@davemloft.net>
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由 Eric Dumazet 提交于
This patch tracks total number of bytes acked for a TCP socket. This is the sum of all changes done to tp->snd_una, and allows for precise tracking of delivered data. RFC4898 named this : tcpEStatsAppHCThruOctetsAcked This is a 64bit field, and can be fetched both from TCP_INFO getsockopt() if one has a handle on a TCP socket, or from inet_diag netlink facility (iproute2/ss patch will follow) Note that tp->bytes_acked was placed near tp->snd_una for best data locality and minimal performance impact. Signed-off-by: NEric Dumazet <edumazet@google.com> Acked-by: NYuchung Cheng <ycheng@google.com> Cc: Matt Mathis <mattmathis@google.com> Cc: Eric Salo <salo@google.com> Cc: Martin Lau <kafai@fb.com> Cc: Chris Rapier <rapier@psc.edu> Signed-off-by: NDavid S. Miller <davem@davemloft.net>
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- 22 4月, 2015 1 次提交
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由 jbaron@akamai.com 提交于
Ensure that we either see that the buffer has write space in tcp_poll() or that we perform a wakeup from the input side. Did not run into any actual problem here, but thought that we should make things explicit. Signed-off-by: NJason Baron <jbaron@akamai.com> Signed-off-by: NDavid S. Miller <davem@davemloft.net>
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- 14 4月, 2015 1 次提交
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由 Kenneth Klette Jonassen 提交于
Since retransmitted segments are not used for RTT estimation, previously SACKed segments present in the rtx queue are used. This estimation can be several times larger than the actual RTT. When a cumulative ack covers both previously SACKed and retransmitted segments, CC may thus get a bogus RTT. Such segments previously had an RTT estimation in tcp_sacktag_one(), so it seems reasonable to not reuse them in tcp_clean_rtx_queue() at all. Afaik, this has had no effect on SRTT/RTO because of Karn's check. Signed-off-by: NKenneth Klette Jonassen <kennetkl@ifi.uio.no> Acked-by: NNeal Cardwell <ncardwell@google.com> Tested-by: NNeal Cardwell <ncardwell@google.com> Acked-by: NYuchung Cheng <ycheng@google.com> Signed-off-by: NDavid S. Miller <davem@davemloft.net>
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- 08 4月, 2015 2 次提交
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由 Daniel Lee 提交于
Fast Open has been using an experimental option with a magic number (RFC6994). This patch makes the client by default use the RFC7413 option (34) to get and send Fast Open cookies. This patch makes the client solicit cookies from a given server first with the RFC7413 option. If that fails to elicit a cookie, then it tries the RFC6994 experimental option. If that also fails, it uses the RFC7413 option on all subsequent connect attempts. If the server returns a Fast Open cookie then the client caches the form of the option that successfully elicited a cookie, and uses that form on later connects when it presents that cookie. The idea is to gradually obsolete the use of experimental options as the servers and clients upgrade, while keeping the interoperability meanwhile. Signed-off-by: NDaniel Lee <Longinus00@gmail.com> Signed-off-by: NYuchung Cheng <ycheng@google.com> Signed-off-by: NNeal Cardwell <ncardwell@google.com> Signed-off-by: NDavid S. Miller <davem@davemloft.net>
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由 Daniel Lee 提交于
Fast Open has been using the experimental option with a magic number (RFC6994) to request and grant Fast Open cookies. This patch enables the server to support the official IANA option 34 in RFC7413 in addition. The change has passed all existing Fast Open tests with both old and new options at Google. Signed-off-by: NDaniel Lee <Longinus00@gmail.com> Signed-off-by: NYuchung Cheng <ycheng@google.com> Signed-off-by: NNeal Cardwell <ncardwell@google.com> Signed-off-by: NDavid S. Miller <davem@davemloft.net>
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- 04 4月, 2015 2 次提交
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由 Ian Morris 提交于
The ipv4 code uses a mixture of coding styles. In some instances check for non-NULL pointer is done as x != NULL and sometimes as x. x is preferred according to checkpatch and this patch makes the code consistent by adopting the latter form. No changes detected by objdiff. Signed-off-by: NIan Morris <ipm@chirality.org.uk> Signed-off-by: NDavid S. Miller <davem@davemloft.net>
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由 Ian Morris 提交于
The ipv4 code uses a mixture of coding styles. In some instances check for NULL pointer is done as x == NULL and sometimes as !x. !x is preferred according to checkpatch and this patch makes the code consistent by adopting the latter form. No changes detected by objdiff. Signed-off-by: NIan Morris <ipm@chirality.org.uk> Signed-off-by: NDavid S. Miller <davem@davemloft.net>
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- 03 4月, 2015 1 次提交
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由 Neal Cardwell 提交于
On processing cumulative ACKs, the FRTO code was not checking the SACKed bit, meaning that there could be a spurious FRTO undo on a cumulative ACK of a previously SACKed skb. The FRTO code should only consider a cumulative ACK to indicate that an original/unretransmitted skb is newly ACKed if the skb was not yet SACKed. The effect of the spurious FRTO undo would typically be to make the connection think that all previously-sent packets were in flight when they really weren't, leading to a stall and an RTO. Signed-off-by: NNeal Cardwell <ncardwell@google.com> Signed-off-by: NYuchung Cheng <ycheng@google.com> Fixes: e33099f9 ("tcp: implement RFC5682 F-RTO") Signed-off-by: NDavid S. Miller <davem@davemloft.net>
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- 30 3月, 2015 1 次提交
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由 Eric Dumazet 提交于
After commit 1fb6f159 ("tcp: add tcp_conn_request"), tcp_syn_flood_action() is no longer used from IPv6. We can make it static, by moving it above tcp_conn_request() Signed-off-by: NEric Dumazet <edumazet@google.com> Reviewed-by: NOctavian Purdila <octavian.purdila@intel.com> Signed-off-by: NDavid S. Miller <davem@davemloft.net>
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- 25 3月, 2015 1 次提交
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由 Eric Dumazet 提交于
ss should display ipv4 mapped request sockets like this : tcp SYN-RECV 0 0 ::ffff:192.168.0.1:8080 ::ffff:192.0.2.1:35261 and not like this : tcp SYN-RECV 0 0 192.168.0.1:8080 192.0.2.1:35261 We should init ireq->ireq_family based on listener sk_family, not the actual protocol carried by SYN packet. This means we can set ireq_family in inet_reqsk_alloc() Fixes: 3f66b083 ("inet: introduce ireq_family") Signed-off-by: NEric Dumazet <edumazet@google.com> Signed-off-by: NDavid S. Miller <davem@davemloft.net>
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- 21 3月, 2015 1 次提交
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由 Eric Dumazet 提交于
When request sock are put in ehash table, the whole notion of having a previous request to update dl_next is pointless. Also, following patch will get rid of big purge timer, so we want to delete a request sock without holding listener lock. Signed-off-by: NEric Dumazet <edumazet@google.com> Signed-off-by: NDavid S. Miller <davem@davemloft.net>
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- 18 3月, 2015 7 次提交
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由 Eric Dumazet 提交于
While testing last patch series, I found req sock refcounting was wrong. We must set skc_refcnt to 1 for all request socks added in hashes, but also on request sockets created by FastOpen or syncookies. It is tricky because we need to defer this initialization so that future RCU lookups do not try to take a refcount on a not yet fully initialized request socket. Also get rid of ireq_refcnt alias. Signed-off-by: NEric Dumazet <edumazet@google.com> Fixes: 13854e5a ("inet: add proper refcounting to request sock") Signed-off-by: NDavid S. Miller <davem@davemloft.net>
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由 Eric Dumazet 提交于
The listener field in struct tcp_request_sock is a pointer back to the listener. We now have req->rsk_listener, so TCP only needs one boolean and not a full pointer. Signed-off-by: NEric Dumazet <edumazet@google.com> Signed-off-by: NDavid S. Miller <davem@davemloft.net>
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由 Eric Dumazet 提交于
Once we'll be able to lookup request sockets in ehash table, we'll need to get access to listener which created this request. This avoid doing a lookup to find the listener, which benefits for a more solid SO_REUSEPORT, and is needed once we no longer queue request sock into a listener private queue. Note that 'struct tcp_request_sock'->listener could be reduced to a single bit, as TFO listener should match req->rsk_listener. TFO will no longer need to hold a reference on the listener. Signed-off-by: NEric Dumazet <edumazet@google.com> Signed-off-by: NDavid S. Miller <davem@davemloft.net>
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由 Eric Dumazet 提交于
inet_reqsk_alloc() is becoming fat and should not be inlined. Signed-off-by: NEric Dumazet <edumazet@google.com> Signed-off-by: NDavid S. Miller <davem@davemloft.net>
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由 Eric Dumazet 提交于
listener socket can be used to set net pointer, and will be later used to hold a reference on listener. Add a const qualifier to first argument (struct request_sock_ops *), and factorize all write_pnet(&ireq->ireq_net, sock_net(sk)); Signed-off-by: NEric Dumazet <edumazet@google.com> Signed-off-by: NDavid S. Miller <davem@davemloft.net>
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由 Eric Dumazet 提交于
tcp_oow_rate_limited() is hardly used in fast path, there is no point inlining it. Signed-of-by: NEric Dumazet <edumazet@google.com> Signed-off-by: NDavid S. Miller <davem@davemloft.net>
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由 Eric Dumazet 提交于
This big helper is called once from tcp_conn_request(), there is no point having it in an include. Compiler will inline it anyway. Signed-off-by: NEric Dumazet <edumazet@google.com> Signed-off-by: NDavid S. Miller <davem@davemloft.net>
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- 15 3月, 2015 1 次提交
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由 Eric Dumazet 提交于
Once request socks will be in ehash table, they will need to have a valid ir_iff field. This is currently true only for IPv6. This patch extends support for IPv4 as well. This means inet_diag_fill_req() can now properly use ir_iif, which is better for IPv6 link locals anyway, as request sockets and established sockets will propagate consistent netlink idiag_if. Signed-off-by: NEric Dumazet <edumazet@google.com> Signed-off-by: NDavid S. Miller <davem@davemloft.net>
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- 13 3月, 2015 1 次提交
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由 Eric Dumazet 提交于
I forgot to update dccp_v6_conn_request() & cookie_v6_check(). They both need to set ireq->ireq_net and ireq->ir_cookie Lets clear ireq->ir_cookie in inet_reqsk_alloc() Signed-off-by: NEric Dumazet <edumazet@google.com> Fixes: 33cf7c90 ("net: add real socket cookies") Signed-off-by: NDavid S. Miller <davem@davemloft.net>
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- 12 3月, 2015 2 次提交
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由 Eric Dumazet 提交于
I forgot to use write_pnet() in three locations. Signed-off-by: NEric Dumazet <edumazet@google.com> Fixes: 33cf7c90 ("net: add real socket cookies") Reported-by: Nkbuild test robot <fengguang.wu@intel.com> Signed-off-by: NDavid S. Miller <davem@davemloft.net>
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由 Eric Dumazet 提交于
A long standing problem in netlink socket dumps is the use of kernel socket addresses as cookies. 1) It is a security concern. 2) Sockets can be reused quite quickly, so there is no guarantee a cookie is used once and identify a flow. 3) request sock, establish sock, and timewait socks for a given flow have different cookies. Part of our effort to bring better TCP statistics requires to switch to a different allocator. In this patch, I chose to use a per network namespace 64bit generator, and to use it only in the case a socket needs to be dumped to netlink. (This might be refined later if needed) Note that I tried to carry cookies from request sock, to establish sock, then timewait sockets. Signed-off-by: NEric Dumazet <edumazet@google.com> Cc: Eric Salo <salo@google.com> Signed-off-by: NDavid S. Miller <davem@davemloft.net>
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- 23 2月, 2015 1 次提交
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由 Neal Cardwell 提交于
tcp_should_expand_sndbuf() does not expand the send buffer if we have filled the congestion window. However, it should use tcp_packets_in_flight() instead of tp->packets_out to make this check. Testing has established that the difference matters a lot if there are many SACKed packets, causing a needless performance shortfall. Signed-off-by: NNeal Cardwell <ncardwell@google.com> Signed-off-by: NYuchung Cheng <ycheng@google.com> Signed-off-by: NEric Dumazet <edumazet@google.com> Signed-off-by: NNandita Dukkipati <nanditad@google.com> Signed-off-by: NDavid S. Miller <davem@davemloft.net>
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- 08 2月, 2015 2 次提交
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由 Neal Cardwell 提交于
Ensure that in state ESTABLISHED, where the connection is represented by a tcp_sock, we rate limit dupacks in response to incoming packets (a) with TCP timestamps that fail PAWS checks, or (b) with sequence numbers or ACK numbers that are out of the acceptable window. We do not send a dupack in response to out-of-window packets if it has been less than sysctl_tcp_invalid_ratelimit (default 500ms) since we last sent a dupack in response to an out-of-window packet. There is already a similar (although global) rate-limiting mechanism for "challenge ACKs". When deciding whether to send a challence ACK, we first consult the new per-connection rate limit, and then the global rate limit. Reported-by: NAvery Fay <avery@mixpanel.com> Signed-off-by: NNeal Cardwell <ncardwell@google.com> Signed-off-by: NYuchung Cheng <ycheng@google.com> Signed-off-by: NEric Dumazet <edumazet@google.com> Signed-off-by: NDavid S. Miller <davem@davemloft.net>
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由 Neal Cardwell 提交于
Helpers for mitigating ACK loops by rate-limiting dupacks sent in response to incoming out-of-window packets. This patch includes: - rate-limiting logic - sysctl to control how often we allow dupacks to out-of-window packets - SNMP counter for cases where we rate-limited our dupack sending The rate-limiting logic in this patch decides to not send dupacks in response to out-of-window segments if (a) they are SYNs or pure ACKs and (b) the remote endpoint is sending them faster than the configured rate limit. We rate-limit our responses rather than blocking them entirely or resetting the connection, because legitimate connections can rely on dupacks in response to some out-of-window segments. For example, zero window probes are typically sent with a sequence number that is below the current window, and ZWPs thus expect to thus elicit a dupack in response. We allow dupacks in response to TCP segments with data, because these may be spurious retransmissions for which the remote endpoint wants to receive DSACKs. This is safe because segments with data can't realistically be part of ACK loops, which by their nature consist of each side sending pure/data-less ACKs to each other. The dupack interval is controlled by a new sysctl knob, tcp_invalid_ratelimit, given in milliseconds, in case an administrator needs to dial this upward in the face of a high-rate DoS attack. The name and units are chosen to be analogous to the existing analogous knob for ICMP, icmp_ratelimit. The default value for tcp_invalid_ratelimit is 500ms, which allows at most one such dupack per 500ms. This is chosen to be 2x faster than the 1-second minimum RTO interval allowed by RFC 6298 (section 2, rule 2.4). We allow the extra 2x factor because network delay variations can cause packets sent at 1 second intervals to be compressed and arrive much closer. Reported-by: NAvery Fay <avery@mixpanel.com> Signed-off-by: NNeal Cardwell <ncardwell@google.com> Signed-off-by: NYuchung Cheng <ycheng@google.com> Signed-off-by: NEric Dumazet <edumazet@google.com> Signed-off-by: NDavid S. Miller <davem@davemloft.net>
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- 04 2月, 2015 2 次提交
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由 Al Viro 提交于
That takes care of the majority of ->sendmsg() instances - most of them via memcpy_to_msg() or assorted getfrag() callbacks. One place where we still keep memcpy_fromiovecend() is tipc - there we potentially read the same data over and over; separate patch, that... Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>
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由 Al Viro 提交于
patch is actually smaller than it seems to be - most of it is unindenting the inner loop body in tcp_sendmsg() itself... the bit in tcp_input.c is going to get reverted very soon - that's what memcpy_from_msg() will become, but not in this commit; let's keep it reasonably contained... There's one potentially subtle change here: in case of short copy from userland, mainline tcp_send_syn_data() discards the skb it has allocated and falls back to normal path, where we'll send as much as possible after rereading the same data again. This patch trims SYN+data skb instead - that way we don't need to copy from the same place twice. Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>
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- 03 2月, 2015 1 次提交
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由 Florian Westphal 提交于
One deployment requirement of DCTCP is to be able to run in a DC setting along with TCP traffic. As Glenn Judd's NSDI'15 paper "Attaining the Promise and Avoiding the Pitfalls of TCP in the Datacenter" [1] (tba) explains, one way to solve this on switch side is to split DCTCP and TCP traffic in two queues per switch port based on the DSCP: one queue soley intended for DCTCP traffic and one for non-DCTCP traffic. For the DCTCP queue, there's the marking threshold K as explained in commit e3118e83 ("net: tcp: add DCTCP congestion control algorithm") for RED marking ECT(0) packets with CE. For the non-DCTCP queue, there's f.e. a classic tail drop queue. As already explained in e3118e83, running DCTCP at scale when not marking SYN/SYN-ACK packets with ECT(0) has severe consequences as for non-ECT(0) packets, traversing the RED marking DCTCP queue will result in a severe reduction of connection probability. This is due to the DCTCP queue being dominated by ECT(0) traffic and switches handle non-ECT traffic in the RED marking queue after passing K as drops, where K is usually a low watermark in order to leave enough tailroom for bursts. Splitting DCTCP traffic among several queues (ECN and non-ECN queue) is being considered a terrible idea in the network community as it splits single flows across multiple network paths. Therefore, commit e3118e83 implements this on Linux as ECT(0) marked traffic, as we argue that marking all packets of a DCTCP flow is the only viable solution and also doesn't speak against the draft. However, recently, a DCTCP implementation for FreeBSD hit also their mainline kernel [2]. In order to let them play well together with Linux' DCTCP, we would need to loosen the requirement that ECT(0) has to be asserted during the 3WHS as not implemented in FreeBSD. This simplifies the ECN test and lets DCTCP work together with FreeBSD. Joint work with Daniel Borkmann. [1] https://www.usenix.org/conference/nsdi15/technical-sessions/presentation/judd [2] https://github.com/freebsd/freebsd/commit/8ad879445281027858a7fa706d13e458095b595fSigned-off-by: NFlorian Westphal <fw@strlen.de> Signed-off-by: NDaniel Borkmann <daniel@iogearbox.net> Cc: Glenn Judd <glenn.judd@morganstanley.com> Signed-off-by: NDavid S. Miller <davem@davemloft.net>
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- 01 2月, 2015 1 次提交
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由 Kenneth Klette Jonassen 提交于
Current behavior only passes RTTs from sequentially acked data to CC. If sender gets a combined ACK for segment 1 and SACK for segment 3, then the computed RTT for CC is the time between sending segment 1 and receiving SACK for segment 3. Pass the minimum computed RTT from any acked data to CC, i.e. time between sending segment 3 and receiving SACK for segment 3. Signed-off-by: NKenneth Klette Jonassen <kennetkl@ifi.uio.no> Signed-off-by: NDavid S. Miller <davem@davemloft.net>
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- 14 1月, 2015 1 次提交
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由 Sébastien Barré 提交于
With TLP, the peer may reply to a probe with an ACK+D-SACK, with ack value set to tlp_high_seq. In the current code, such ACK+DSACK will be missed and only at next, higher ack will the TLP episode be considered done. Since the DSACK is not present anymore, this will cost a cwnd reduction. This patch ensures that this scenario does not cause a cwnd reduction, since receiving an ACK+DSACK indicates that both the initial segment and the probe have been received by the peer. The following packetdrill test, from Neal Cardwell, validates this patch: // Establish a connection. 0 socket(..., SOCK_STREAM, IPPROTO_TCP) = 3 +0 setsockopt(3, SOL_SOCKET, SO_REUSEADDR, [1], 4) = 0 +0 bind(3, ..., ...) = 0 +0 listen(3, 1) = 0 +0 < S 0:0(0) win 32792 <mss 1000,sackOK,nop,nop,nop,wscale 7> +0 > S. 0:0(0) ack 1 <mss 1460,nop,nop,sackOK,nop,wscale 6> +.020 < . 1:1(0) ack 1 win 257 +0 accept(3, ..., ...) = 4 // Send 1 packet. +0 write(4, ..., 1000) = 1000 +0 > P. 1:1001(1000) ack 1 // Loss probe retransmission. // packets_out == 1 => schedule PTO in max(2*RTT, 1.5*RTT + 200ms) // In this case, this means: 1.5*RTT + 200ms = 230ms +.230 > P. 1:1001(1000) ack 1 +0 %{ assert tcpi_snd_cwnd == 10 }% // Receiver ACKs at tlp_high_seq with a DSACK, // indicating they received the original packet and probe. +.020 < . 1:1(0) ack 1001 win 257 <sack 1:1001,nop,nop> +0 %{ assert tcpi_snd_cwnd == 10 }% // Send another packet. +0 write(4, ..., 1000) = 1000 +0 > P. 1001:2001(1000) ack 1 // Receiver ACKs above tlp_high_seq, which should end the TLP episode // if we haven't already. We should not reduce cwnd. +.020 < . 1:1(0) ack 2001 win 257 +0 %{ assert tcpi_snd_cwnd == 10, tcpi_snd_cwnd }% Credits: -Gregory helped in finding that tcp_process_tlp_ack was where the cwnd got reduced in our MPTCP tests. -Neal wrote the packetdrill test above -Yuchung reworked the patch to make it more readable. Cc: Gregory Detal <gregory.detal@uclouvain.be> Cc: Nandita Dukkipati <nanditad@google.com> Tested-by: NNeal Cardwell <ncardwell@google.com> Reviewed-by: NYuchung Cheng <ycheng@google.com> Reviewed-by: NEric Dumazet <eric.dumazet@gmail.com> Signed-off-by: NSébastien Barré <sebastien.barre@uclouvain.be> Acked-by: NEric Dumazet <edumazet@google.com> Acked-by: NNeal Cardwell <ncardwell@google.com> Signed-off-by: NDavid S. Miller <davem@davemloft.net>
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- 10 12月, 2014 1 次提交
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由 Al Viro 提交于
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>
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- 24 11月, 2014 1 次提交
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由 Al Viro 提交于
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>
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