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* [SK_BUFF]: Use skb_reset_network_header after skb_pushArnaldo Carvalho de Melo2007-04-252-11/+12
| | | | | | | | Some more cases where skb->nh.iph was being set that were converted to using skb_reset_network_header. Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com> Signed-off-by: David S. Miller <davem@davemloft.net>
* [SK_BUFF] ipconfig: Another conversion to skb_reset_network_header related ↵Arnaldo Carvalho de Melo2007-04-251-1/+2
| | | | | | | | | | to skb_put boot_pkt->iph is the first member, that is at skb->data, so just use skb_reset_network_header(). Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com> Signed-off-by: David S. Miller <davem@davemloft.net>
* [SK_BUFF]: Some more skb_put cases converted to skb_reset_network_headerArnaldo Carvalho de Melo2007-04-252-3/+5
| | | | | Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com> Signed-off-by: David S. Miller <davem@davemloft.net>
* [SK_BUFF]: Some more simple skb_reset_network_header conversionsArnaldo Carvalho de Melo2007-04-251-2/+2
| | | | | | | | | | | | | | | This time of the type: skb->nh.iph = (struct iphdr *)skb->data; That is completely equivalent to: skb->nh.raw = skb->data; Wonder why people love casts... :-) Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com> Signed-off-by: David S. Miller <davem@davemloft.net>
* [SK_BUFF]: Use skb_reset_network_header where the return of __pskb_pull was ↵Arnaldo Carvalho de Melo2007-04-251-1/+2
| | | | | | | | | being used It returns skb->data, so we can just use skb_reset_network_header after it. Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com> Signed-off-by: David S. Miller <davem@davemloft.net>
* [SK_BUFF]: Use skb_reset_network_header where the skb_pull return was being usedArnaldo Carvalho de Melo2007-04-252-3/+9
| | | | | | | | | But only in the cases where its a newly allocated skb, i.e. one where skb->tail is equal to skb->data, or just after skb_reserve, where this requirement is maintained. Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com> Signed-off-by: David S. Miller <davem@davemloft.net>
* [SK_BUFF]: Use skb_reset_network_header in skb_push casesArnaldo Carvalho de Melo2007-04-258-8/+17
| | | | | | | | skb_push updates and returns skb->data, so we can just call skb_reset_network_header after the call to skb_push. Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com> Signed-off-by: David S. Miller <davem@davemloft.net>
* [SK_BUFF]: Introduce skb_reset_network_header(skb)Arnaldo Carvalho de Melo2007-04-256-8/+8
| | | | | | | | | | | | For the common, open coded 'skb->nh.raw = skb->data' operation, so that we can later turn skb->nh.raw into a offset, reducing the size of struct sk_buff in 64bit land while possibly keeping it as a pointer on 32bit. This one touches just the most simple case, next will handle the slightly more "complex" cases. Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com> Signed-off-by: David S. Miller <davem@davemloft.net>
* [SK_BUFF]: Introduce skb_mac_header()Arnaldo Carvalho de Melo2007-04-255-9/+9
| | | | | | | | | | | | For the places where we need a pointer to the mac header, it is still legal to touch skb->mac.raw directly if just adding to, subtracting from or setting it to another layer header. This one also converts some more cases to skb_reset_mac_header() that my regex missed as it had no spaces before nor after '=', ugh. Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com> Signed-off-by: David S. Miller <davem@davemloft.net>
* [TCP]: Use skb_set_mac_header in tcp_collapseArnaldo Carvalho de Melo2007-04-251-1/+1
| | | | | Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com> Signed-off-by: David S. Miller <davem@davemloft.net>
* [TCP]: Do the layer header setting in tcp_collapse relative to skb->dataArnaldo Carvalho de Melo2007-04-251-3/+5
| | | | | | | | That is equal to skb->head before skb_reserve, to help in the layer header changes. Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com> Signed-off-by: David S. Miller <davem@davemloft.net>
* [SK_BUFF] xfrm: Use skb_set_mac_header in the memmove casesArnaldo Carvalho de Melo2007-04-251-2/+4
| | | | | Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com> Signed-off-by: David S. Miller <davem@davemloft.net>
* [SK_BUFF]: Introduce skb_reset_mac_header(skb)Arnaldo Carvalho de Melo2007-04-253-3/+4
| | | | | | | | | | | | For the common, open coded 'skb->mac.raw = skb->data' operation, so that we can later turn skb->mac.raw into a offset, reducing the size of struct sk_buff in 64bit land while possibly keeping it as a pointer on 32bit. This one touches just the most simple case, next will handle the slightly more "complex" cases. Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com> Signed-off-by: David S. Miller <davem@davemloft.net>
* [UDP]: Use __skb_pull since we have checked it won't fail with pskb_may_pullArnaldo Carvalho de Melo2007-04-251-1/+1
| | | | | Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com> Signed-off-by: David S. Miller <davem@davemloft.net>
* [UDP]: deinlineStephen Hemminger2007-04-251-4/+4
| | | | | | | | A couple of functions are exported or used indirectly so it is pointless to mark them as inline. Signed-off-by: Stephen Hemminger <shemminger@linux-foundation.org> Signed-off-by: David S. Miller <davem@davemloft.net>
* [TCP]: whitespace cleanupStephen Hemminger2007-04-255-50/+51
| | | | | | | Add whitespace around keywords. Signed-off-by: Stephen Hemminger <shemminger@linux-foundation.org> Signed-off-by: David S. Miller <davem@davemloft.net>
* [IPV4]: cleanupStephen Hemminger2007-04-2512-750/+745
| | | | | | | Add whitespace around keywords. Signed-off-by: Stephen Hemminger <shemminger@linux-foundation.org> Signed-off-by: David S. Miller <davem@davemloft.net>
* [UDP]: ipv4 whitespace cleanupStephen Hemminger2007-04-251-47/+48
| | | | | | | Fix whitespace around keywords. Signed-off-by: Stephen Hemminger <shemminger@linux-foundation.org> Signed-off-by: David S. Miller <davem@davemloft.net>
* [NET]: Introduce SIOCGSTAMPNS ioctl to get timestamps with nanosec resolutionEric Dumazet2007-04-251-0/+3
| | | | | | | | | | Now network timestamps use ktime_t infrastructure, we can add a new ioctl() SIOCGSTAMPNS command to get timestamps in 'struct timespec'. User programs can thus access to nanosecond resolution. Signed-off-by: Eric Dumazet <dada1@cosmosbay.com> CC: Stephen Hemminger <shemminger@linux-foundation.org> Signed-off-by: David S. Miller <davem@davemloft.net>
* [TCP]: Abstract out all write queue operations.David S. Miller2007-04-255-96/+107
| | | | | | | This allows the write queue implementation to be changed, for example, to one which allows fast interval searching. Signed-off-by: David S. Miller <davem@davemloft.net>
* [NET] IPV4: Use hton{s,l}() where appropriate.YOSHIFUJI Hideaki2007-04-254-26/+25
| | | | | Signed-off-by: YOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org> Signed-off-by: David S. Miller <davem@davemloft.net>
* [UDP]: Clean up UDP-Lite receive checksumHerbert Xu2007-04-252-48/+50
| | | | | | | | | | | | | | | | | | | | | | This patch eliminates some duplicate code for the verification of receive checksums between UDP-Lite and UDP. It does this by introducing __skb_checksum_complete_head which is identical to __skb_checksum_complete_head apart from the fact that it takes a length parameter rather than computing the first skb->len bytes. As a result UDP-Lite will be able to use hardware checksum offload for packets which do not use partial coverage checksums. It also means that UDP-Lite loopback no longer does unnecessary checksum verification. If any NICs start support UDP-Lite this would also start working automatically. This patch removes the assumption that msg_flags has MSG_TRUNC clear upon entry in recvmsg. Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au> Signed-off-by: David S. Miller <davem@davemloft.net>
* [IPV4]: Optimize inet_getpeer()Eric Dumazet2007-04-251-16/+22
| | | | | | | | | | | | | | | | 1) Some sysctl vars are declared __read_mostly 2) We can avoid updating stack[] when doing an AVL lookup only. lookup() macro is extended to receive a second parameter, that may be NULL in case of a pure lookup (no need to save the AVL path). This removes unnecessary instructions, because compiler knows if this _stack parameter is NULL or not. text size of net/ipv4/inetpeer.o is 2063 bytes instead of 2107 on x86_64 Signed-off-by: Eric Dumazet <dada1@cosmosbay.com> Signed-off-by: David S. Miller <davem@davemloft.net>
* [TCP] TCP Yeah: cleanupStephen Hemminger2007-04-251-19/+23
| | | | | | | | | Eliminate need for full 6/4/64 divide to compute queue. Variable maxqueue was really a constant. Fix indentation. Signed-off-by: Stephen Hemminger <shemminger@linux-foundation.org> Signed-off-by: David S. Miller <davem@davemloft.net>
* [TCP] tcp_cubic: faster cube rootStephen Hemminger2007-04-251-11/+5
| | | | | | | | | | | | The Newton-Raphson method is quadratically convergent so only a small fixed number of steps are necessary. Therefore it is faster to unroll the loop. Since div64_64 is no longer inline it won't cause code explosion. Also fixes a bug that can occur if x^2 was bigger than 32 bits. Signed-off-by: Stephen Hemminger <shemminger@linux-foundation.org> Signed-off-by: David S. Miller <davem@davemloft.net>
* [NET]: convert network timestamps to ktime_tEric Dumazet2007-04-253-9/+13
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 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: David S. Miller <davem@davemloft.net>
* [NET]: div64_64 consolidate (rev3)Stephen Hemminger2007-04-253-44/+1
| | | | | | | Here is the current version of the 64 bit divide common code. Signed-off-by: Stephen Hemminger <shemminger@linux-foundation.org> Signed-off-by: David S. Miller <davem@davemloft.net>
* [NET]: Convert xtime.tv_sec to get_seconds()James Morris2007-04-254-13/+13
| | | | | | | | 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: David S. Miller <davem@davemloft.net>
* [TCP]: FRTO undo response falls back to ratehalving one if ECEdIlpo Järvinen2007-04-251-5/+6
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 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: David S. Miller <davem@davemloft.net>
* [TCP]: Complete icsk-to-local-variable change (in tcp_enter_cwr)Ilpo Järvinen2007-04-251-1/+1
| | | | | | | | A local variable for icsk was created but this change was missing. Spotted by Jarek Poplawski. Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi> Signed-off-by: David S. Miller <davem@davemloft.net>
* [TCP]: Add two new spurious RTO responses to FRTOIlpo Järvinen2007-04-253-5/+41
| | | | | | | | | | | | | | | | | 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: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi> Signed-off-by: David S. Miller <davem@davemloft.net>
* [TCP]: Correct reordering detection change (no FRTO case)Ilpo Järvinen2007-04-251-1/+1
| | | | | | | | | 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: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi> Signed-off-by: David S. Miller <davem@davemloft.net>
* [TCP]: Keep copied_seq, rcv_wup and rcv_next together.Eric Dumazet2007-04-251-4/+2
| | | | | | | | | | | | | | | | | | | | | | | | | | | | 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: Eric Dumazet <dada1@cosmosbay.com> Signed-off-by: David S. Miller <davem@davemloft.net>
* [TCP]: struct *sock argument renamed: sp -> skIlpo Järvinen2007-04-251-11/+11
| | | | | | | In general, TCP code uses "sk" for struct sock pointer. Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi> Signed-off-by: David S. Miller <davem@davemloft.net>
* [TCP]: Add RFC3742 Limited Slow-Start, controlled by variable ↵John Heffner2007-04-252-9/+30
| | | | | | | sysctl_tcp_max_ssthresh. Signed-off-by: John Heffner <jheffner@psc.edu> Signed-off-by: David S. Miller <davem@davemloft.net>
* [TCP] YeAH-TCP: algorithm implementationAngelo P. Castellani2007-04-254-0/+437
| | | | | | | | | | | | | | 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.pdf Signed-off-by: Angelo P. Castellani <angelo.castellani@gmail.con> Signed-off-by: David S. Miller <davem@davemloft.net>
* [TCP]: SACK enhanced FRTOIlpo Järvinen2007-04-251-11/+65
| | | | | | | | | | | | | | | | | | | 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: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi> Signed-off-by: David S. Miller <davem@davemloft.net>
* [TCP]: Prevent reordering adjustments during FRTOIlpo Järvinen2007-04-251-1/+2
| | | | | | | | | | | | 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: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi> Signed-off-by: David S. Miller <davem@davemloft.net>
* [TCP] FRTO: Fake cwnd for ssthresh callbackIlpo Järvinen2007-04-251-1/+25
| | | | | | | | | | | | | | | | | | 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: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi> Signed-off-by: David S. Miller <davem@davemloft.net>
* [TCP] FRTO: Reverse RETRANS bit clearing logicIlpo Järvinen2007-04-251-12/+23
| | | | | | | | | | | | | | | | | | | | | | 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: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi> Signed-off-by: David S. Miller <davem@davemloft.net>
* [TCP] FRTO: Entry is allowed only during (New)Reno like recoveryIlpo Järvinen2007-04-251-4/+21
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 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 <ilpo.jarvinen@helsinki.fi> Signed-off-by: David S. Miller <davem@davemloft.net>
* [TCP]: Prevent unrelated cwnd adjustment while using FRTOIlpo Järvinen2007-04-251-7/+11
| | | | | | | | | | 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: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi> Signed-off-by: David S. Miller <davem@davemloft.net>
* [TCP] FRTO: frto_counter modulo-op converted to two assignmentsIlpo Järvinen2007-04-251-2/+2
| | | | | Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi> Signed-off-by: David S. Miller <davem@davemloft.net>
* [TCP]: Don't enter to fast recovery while using FRTOIlpo Järvinen2007-04-251-0/+4
| | | | | | | | | | | | | | 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: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi> Signed-off-by: David S. Miller <davem@davemloft.net>
* [TCP] FRTO: Response should reset also snd_cwnd_cntIlpo Järvinen2007-04-251-0/+1
| | | | | | | | 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: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi> Signed-off-by: David S. Miller <davem@davemloft.net>
* [TCP] FRTO: fixes fallback to conventional recoveryIlpo Järvinen2007-04-251-5/+9
| | | | | | | | | | | | | | | | | | | | | | | | | | 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: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi> Signed-off-by: David S. Miller <davem@davemloft.net>
* [TCP] FRTO: Ignore some uninteresting ACKsIlpo Järvinen2007-04-251-3/+10
| | | | | | | | | 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: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi> Signed-off-by: David S. Miller <davem@davemloft.net>
* [TCP] FRTO: Use Disorder state during operation instead of OpenIlpo Järvinen2007-04-251-3/+3
| | | | | | | | | | | | | | | | | | | | | | | 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: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi> Signed-off-by: David S. Miller <davem@davemloft.net>
* [TCP] FRTO: Consecutive RTOs keep prior_ssthresh and ssthreshIlpo Järvinen2007-04-251-6/+14
| | | | | | | | | | | | | | 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: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi> Signed-off-by: David S. Miller <davem@davemloft.net>
* [TCP] FRTO: Comment cleanup & improvementIlpo Järvinen2007-04-251-17/+32
| | | | | | | | | | | | 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: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi> Signed-off-by: David S. Miller <davem@davemloft.net>
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