- 26 Apr, 2007 40 commits
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Yasuyuki Kozakai authored
Signed-off-by:
Yasuyuki Kozakai <yasuyuki.kozakai@toshiba.co.jp> Signed-off-by:
YOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org> Signed-off-by:
David S. Miller <davem@davemloft.net>
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Yasuyuki Kozakai authored
Some notes - Protocol number IPPROTO_IPIP is used for IPv4 over IPv6 packets. - If IP6_TNL_F_USE_ORIG_TCLASS is set, TOS in IPv4 header is copied to Traffic Class in outer IPv6 header on xmit. - IP6_TNL_F_USE_ORIG_FLOWLABEL is ignored on xmit of IPv4 packets, because IPv4 header does not have flow label. - Kernel sends ICMP error if IPv4 packet is too big on xmit, even if DF flag is not set. Signed-off-by:
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Yasuyuki Kozakai authored
This enables to add IPv4/IPv6 specific handling later, Signed-off-by:
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Yasuyuki Kozakai authored
This enables to add IPv4/IPv6 specific handling later, Signed-off-by:
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Yasuyuki Kozakai authored
This enables to add IPv4/IPv6 specific error handling later, Signed-off-by:
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YOSHIFUJI Hideaki authored
Signed-off-by: -
David S. Miller authored
If the user passes MSG_TRUNC in via msg_flags, return the full packet size not the truncated size. Idea from Herbert Xu and Thomas Graf. Signed-off-by: -
Eric Dumazet authored
We currently use a special structure (struct skb_timeval) and plain 'struct timeval' to store packet timestamps in sk_buffs and struct sock. This has some drawbacks : - Fixed resolution of micro second. - Waste of space on 64bit platforms where sizeof(struct timeval)=16 I suggest using ktime_t that is a nice abstraction of high resolution time services, currently capable of nanosecond resolution. As sizeof(ktime_t) is 8 bytes, using ktime_t in 'struct sock' permits a 8 byte shrink of this structure on 64bit architectures. Some other structures also benefit from this size reduction (struct ipq in ipv4/ip_fragment.c, struct frag_queue in ipv6/reassembly.c, ...) Once this ktime infrastructure adopted, we can more easily provide nanosecond resolution on top of it. (ioctl SIOCGSTAMPNS and/or SO_TIMESTAMPNS/SCM_TIMESTAMPNS) Note : this patch includes a bug correction in compat_sock_get_timestamp() where a "err = 0;" was missing (so this syscall returned -ENOENT instead of 0) Signed-off-by:
Eric Dumazet <dada1@cosmosbay.com> CC: Stephen Hemminger <shemminger@linux-foundation.org> CC: John find <linux.kernel@free.fr> Signed-off-by:
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Stephen Hemminger authored
Here is the current version of the 64 bit divide common code. Signed-off-by:
Stephen Hemminger <shemminger@linux-foundation.org> Signed-off-by:
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James Morris authored
Where appropriate, convert references to xtime.tv_sec to the get_seconds() helper function. Signed-off-by:
James Morris <jmorris@namei.org> Signed-off-by:
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Stephen Hemminger authored
Since devices can change name and other wierdness, don't hold onto a copy of device name, instead use pointer to output device. Fix a couple of leaks in error handling path as well. Signed-off-by:
Robert Olsson <robert.olsson@its.uu.se> Signed-off-by:
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Stephen Hemminger authored
The existing htonl() macro is smart enough to do the same code as using __constant_htonl() and it looks cleaner. Signed-off-by:
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Stephen Hemminger authored
Can use random32() now. Signed-off-by:
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Stephen Hemminger authored
Remove private debug macro and replace with standard version Signed-off-by:
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Eric Dumazet authored
sk_backlog is a critical field of struct sock. (known famous words) It is (ab)used in hot paths, in particular in release_sock(), tcp_recvmsg(), tcp_v4_rcv(), sk_receive_skb(). It really makes sense to place it next to sk_lock, because sk_backlog is only used after sk_lock locked (and thus memory cache line in L1 cache). This should reduce cache misses and sk_lock acquisition time. (In theory, we could only move the head pointer near sk_lock, and leaving tail far away, because 'tail' is normally not so hot, but keep it simple :) ) Signed-off-by:
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Ilpo Järvinen authored
Undoing ssthresh is disabled in fastretrans_alert whenever FLAG_ECE is set by clearing prior_ssthresh. The clearing does not protect FRTO because FRTO operates before fastretrans_alert. Moving the clearing of prior_ssthresh earlier seems to be a suboptimal solution to the FRTO case because then FLAG_ECE will cause a second ssthresh reduction in try_to_open (the first occurred when FRTO was entered). So instead, FRTO falls back immediately to the rate halving response, which switches TCP to CA_CWR state preventing the latter reduction of ssthresh. If the first ECE arrived before the ACK after which FRTO is able to decide RTO as spurious, prior_ssthresh is already cleared. Thus no undoing for ssthresh occurs. Besides, FLAG_ECE should be set also in the following ACKs resulting in rate halving response that sees TCP is already in CA_CWR, which again prevents an extra ssthresh reduction on that round-trip. If the first ECE arrived before RTO, ssthresh has already been adapted and prior_ssthresh remains cleared on entry because TCP is in CA_CWR (the same applies also to a case where FRTO is entered more than once and ECE comes in the middle). High_seq must not be touched after tcp_enter_cwr because CWR round-trip calculation depends on it. I believe that after this patch, FRTO should be ECN-safe and even able to take advantage of synergy benefits. Signed-off-by:
Ilpo Järvinen <ilpo.jarvinen@helsinki.fi> Signed-off-by:
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Ilpo Järvinen authored
A local variable for icsk was created but this change was missing. Spotted by Jarek Poplawski. Signed-off-by:
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Ilpo Järvinen authored
In addition, fixed minor things in tcp_frto sysctl. Signed-off-by:
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Ilpo Järvinen authored
New sysctl tcp_frto_response is added to select amongst these responses: - Rate halving based; reuses CA_CWR state (default) - Very conservative; used to be the only one available (=1) - Undo cwr; undoes ssthresh and cwnd reductions (=2) The response with rate halving requires a new parameter to tcp_enter_cwr because FRTO has already reduced ssthresh and doing a second reduction there has to be prevented. In addition, to keep things nice on 80 cols screen, a local variable was added. Signed-off-by:
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Ilpo Järvinen authored
The reordering detection must work also when FRTO has not been used at all which was the original intention of mine, just the expression of the idea was flawed. Signed-off-by:
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David S. Miller authored
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Eric Dumazet authored
I noticed in oprofile study a cache miss in tcp_rcv_established() to read copied_seq. ffffffff80400a80 <tcp_rcv_established>: /* tcp_rcv_established total: 4034293 2.0400 */ 55493 0.0281 :ffffffff80400bc9: mov 0x4c8(%r12),%eax copied_seq 543103 0.2746 :ffffffff80400bd1: cmp 0x3e0(%r12),%eax rcv_nxt if (tp->copied_seq == tp->rcv_nxt && len - tcp_header_len <= tp->ucopy.len) { In this function, the cache line 0x4c0 -> 0x500 is used only for this reading 'copied_seq' field. rcv_wup and copied_seq should be next to rcv_nxt field, to lower number of active cache lines in hot paths. (tcp_rcv_established(), tcp_poll(), ...) As you suggested, I changed tcp_create_openreq_child() so that these fields are changed together, to avoid adding a new store buffer stall. Patch is 64bit friendly (no new hole because of alignment constraints) Signed-off-by: -
Ilpo Järvinen authored
In general, TCP code uses "sk" for struct sock pointer. Signed-off-by:
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John Heffner authored
Signed-off-by:
John Heffner <jheffner@psc.edu> Signed-off-by:
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Angelo P. Castellani authored
YeAH-TCP is a sender-side high-speed enabled TCP congestion control algorithm, which uses a mixed loss/delay approach to compute the congestion window. It's design goals target high efficiency, internal, RTT and Reno fairness, resilience to link loss while keeping network elements load as low as possible. For further details look here: http://wil.cs.caltech.edu/pfldnet2007/paper/YeAH_TCP.pdfSigned-off-by:Angelo P. Castellani <angelo.castellani@gmail.con> Signed-off-by:
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Ilpo Järvinen authored
The description is overly verbose to avoid ambiguity between "SACK enabled" and "SACK enhanced FRTO" Signed-off-by:
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Ilpo Järvinen authored
Implements the SACK-enhanced FRTO given in RFC4138 using the variant given in Appendix B. RFC4138, Appendix B: "This means that in order to declare timeout spurious, the TCP sender must receive an acknowledgment for non-retransmitted segment between SND.UNA and RecoveryPoint in algorithm step 3. RecoveryPoint is defined in conservative SACK-recovery algorithm [RFC3517]" The basic version of the FRTO algorithm can still be used also when SACK is enabled. To enabled SACK-enhanced version, tcp_frto sysctl is set to 2. Signed-off-by:
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Ilpo Järvinen authored
To be honest, I'm not too sure how the reord stuff works in the first place but this seems necessary. When FRTO has been active, the one and only retransmission could be unnecessary but the state and sending order might not be what the sacktag code expects it to be (to work correctly). Signed-off-by:
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Ilpo Järvinen authored
TCP without FRTO would be in Loss state with small cwnd. FRTO, however, leaves cwnd (typically) to a larger value which causes ssthresh to become too large in case RTO is triggered again compared to what conventional recovery would do. Because consecutive RTOs result in only a single ssthresh reduction, RTO+cumulative ACK+RTO pattern is required to trigger this event. A large comment is included for congestion control module writers trying to figure out what CA_EVENT_FRTO handler should do because there exists a remote possibility of incompatibility between FRTO and module defined ssthresh functions. Signed-off-by:
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Ilpo Järvinen authored
Previously RETRANS bits were cleared on the entry to FRTO. We postpone that into tcp_enter_frto_loss, which is really the place were the clearing should be done anyway. This allows simplification of the logic from a clearing loop to the head skb clearing only. Besides, the other changes made in the previous patches to tcp_use_frto made it impossible for the non-SACKed FRTO to be entered if other than the head has been rexmitted. With SACK-enhanced FRTO (and Appendix B), however, there can be a number retransmissions in flight when RTO expires (same thing could happen before this patchset also with non-SACK FRTO). To not introduce any jumpiness into the packet counting during FRTO, instead of clearing RETRANS bits from skbs during entry, do it later on. Signed-off-by:
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Ilpo Järvinen authored
This interpretation comes from RFC4138: "If the sender implements some loss recovery algorithm other than Reno or NewReno [FHG04], the F-RTO algorithm SHOULD NOT be entered when earlier fast recovery is underway." I think the RFC means to say (especially in the light of Appendix B) that ...recovery is underway (not just fast recovery) or was underway when it was interrupted by an earlier (F-)RTO that hasn't yet been resolved (snd_una has not advanced enough). Thus, my interpretation is that whenever TCP has ever retransmitted other than head, basic version cannot be used because then the order assumptions which are used as FRTO basis do not hold. NewReno has only the head segment retransmitted at a time. Therefore, walk up to the segment that has not been SACKed, if that segment is not retransmitted nor anything before it, we know for sure, that nothing after the non-SACKed segment should be either. This assumption is valid because TCPCB_EVER_RETRANS does not leave holes but each non-SACKed segment is rexmitted in-order. Check for retrans_out > 1 avoids more expensive walk through the skb list, as we can know the result beforehand: F-RTO will not be allowed. SACKed skb can turn into non-SACked only in the extremely rare case of SACK reneging, in this case we might fail to detect retransmissions if there were them for any other than head. To get rid of that feature, whole rexmit queue would have to be walked (always) or FRTO should be prevented when SACK reneging happens. Of course RTO should still trigger after reneging which makes this issue even less likely to show up. And as long as the response is as conservative as it's now, nothing bad happens even then. Signed-off-by: -
Ilpo Järvinen authored
FRTO controls cwnd when it still processes the ACK input or it has just reverted back to conventional RTO recovery; the normal rules apply when FRTO has reverted to standard congestion control. Signed-off-by:
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Ilpo Järvinen authored
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Ilpo Järvinen authored
Because TCP is not in Loss state during FRTO recovery, fast recovery could be triggered by accident. Non-SACK FRTO is more robust than not yet included SACK-enhanced version (that can receiver high number of duplicate ACKs with SACK blocks during FRTO), at least with unidirectional transfers, but under extraordinary patterns fast recovery can be incorrectly triggered, e.g., Data loss+ACK losses => cumulative ACK with enough SACK blocks to meet sacked_out >= dupthresh condition). Signed-off-by:
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Ilpo Järvinen authored
Since purpose is to reduce CWND, we prevent immediate growth. This is not a major issue nor is "the correct way" specified anywhere. Signed-off-by:
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Ilpo Järvinen authored
The FRTO detection did not care how ACK pattern affects to cwnd calculation of the conventional recovery. This caused incorrect setting of cwnd when the fallback becames necessary. The knowledge tcp_process_frto() has about the incoming ACK is now passed on to tcp_enter_frto_loss() in allowed_segments parameter that gives the number of segments that must be added to packets-in-flight while calculating the new cwnd. Instead of snd_una we use FLAG_DATA_ACKED in duplicate ACK detection because RFC4138 states (in Section 2.2): If the first acknowledgment after the RTO retransmission does not acknowledge all of the data that was retransmitted in step 1, the TCP sender reverts to the conventional RTO recovery. Otherwise, a malicious receiver acknowledging partial segments could cause the sender to declare the timeout spurious in a case where data was lost. If the next ACK after RTO is duplicate, we do not retransmit anything, which is equal to what conservative conventional recovery does in such case. Signed-off-by:
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Ilpo Järvinen authored
Handles RFC4138 shortcoming (in step 2); it should also have case c) which ignores ACKs that are not duplicates nor advance window (opposite dir data, winupdate). Signed-off-by:
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Ilpo Järvinen authored
Retransmission counter assumptions are to be changed. Forcing reason to do this exist: Using sysctl in check would be racy as soon as FRTO starts to ignore some ACKs (doing that in the following patches). Userspace may disable it at any moment giving nice oops if timing is right. frto_counter would be inaccessible from userspace, but with SACK enhanced FRTO retrans_out can include other than head, and possibly leaving it non-zero after spurious RTO, boom again. Luckily, solution seems rather simple: never go directly to Open state but use Disorder instead. This does not really change much, since TCP could anyway change its state to Disorder during FRTO using path tcp_fastretrans_alert -> tcp_try_to_open (e.g., when a SACK block makes ACK dubious). Besides, Disorder seems to be the state where TCP should be if not recovering (in Recovery or Loss state) while having some retransmissions in-flight (see tcp_try_to_open), which is exactly what happens with FRTO. Signed-off-by:
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Ilpo Järvinen authored
In case a latency spike causes more than one RTO, the later should not cause the already reduced ssthresh to propagate into the prior_ssthresh since FRTO declares all such RTOs spurious at once or none of them. In treating of ssthresh, we mimic what tcp_enter_loss() does. The previous state (in frto_counter) must be available until we have checked it in tcp_enter_frto(), and also ACK information flag in process_frto(). Signed-off-by:
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Ilpo Järvinen authored
Moved comments out from the body of process_frto() to the head (preferred way; see Documentation/CodingStyle). Bonus: it's much easier to read in this compacted form. FRTO algorithm and implementation is described in greater detail. For interested reader, more information is available in RFC4138. Signed-off-by:
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