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2007-10-10[DCCP]: Send Reset upon Sync in state REQUESTGerrit Renker1-5/+3
This fixes the code to correspond to RFC 4340, 7.5.4, which states the exception that a Sync received in state REQUEST generates a Reset (not a SyncAck). To achieve this, only a small change is required. Since dccp_rcv_request_sent_state_process() already uses the correct Reset Code number 4 ("Packet Error"), we only need to shift the if-statement a few lines further down. (To test this case: replace DCCP_PKT_RESPONSE with DCCP_PKT_SYNC in dccp_make_response.) Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk> Signed-off-by: Ian McDonald <ian.mcdonald@jandi.co.nz> Signed-off-by: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
2007-10-10[BLUETOOTH]: Make hidp_setup_input() return intWANG Cong1-4/+7
This patch: - makes hidp_setup_input() return int to indicate errors; - checks its return value to handle errors. And this time it is against -rc7-mm1 tree. Thanks to roel and Marcel Holtmann for comments. Signed-off-by: WANG Cong <xiyou.wangcong@gmail.com> Signed-off-by: Marcel Holtmann <marcel@holtmann.org> Signed-off-by: David S. Miller <davem@davemloft.net>
2007-10-10[TCP] MIB: Count FRTO's successfully detected spurious RTOsIlpo Järvinen3-0/+3
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi> Signed-off-by: David S. Miller <davem@davemloft.net>
2007-10-10[TCP]: Reordered ACK's (old) SACKs not included to discarded MIBIlpo Järvinen1-1/+6
In case of ACK reordering, the SACK block might be valid in it's time but is already obsoleted since we've received another kind of confirmation about arrival of the segments through snd_una advancement of an earlier packet. I didn't bother to build distinguishing of valid and invalid SACK blocks but simply made reordered SACK blocks that are too old always not counted regardless of their "real" validity which could be determined by using the ack field of the reordered packet (won't be significant IMHO). DSACKs can very well be considered useful even in this situation, so won't do any of this for them. Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi> Signed-off-by: David S. Miller <davem@davemloft.net>
2007-10-10[TCP]: Re-place highest_sack check to a more robust positionIlpo Järvinen1-4/+4
I previously added checking to position that is rather poor as state has already been adjusted quite a bit. Re-placing it above all state changes should be more robust though the return should never ever get executed regardless of its place :-). Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi> Signed-off-by: David S. Miller <davem@davemloft.net>
2007-10-10[DCCP]: Parameter renamingGerrit Renker1-4/+6
The parameter `seq' of dccp_send_sync() is in fact an acknowledgement number and not a sequence number - thus renamed by this patch into `ackno'. Secondly, a `critical' warning is added when a Sync/SyncAck could not be sent. Sanity: I have checked all other functions that are called in dccp_transmit_skb, there are no clashes with the use of dccpd_ack_seq; no other function is using this slot at the same time. Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk> Signed-off-by: Ian McDonald <ian.mcdonald@jandi.co.nz> Signed-off-by: Arnaldo Carvalho de Melo <acme@ghostprotocols.net> Signed-off-by: David S. Miller <davem@davemloft.net>
2007-10-10[DCCP]: Fix Reset/Sync-Flood BugGerrit Renker1-3/+11
This updates sequence number checking with regard to RFC 4340, 7.5.4. Missing in the code was an exception for sequence-invalid Reset packets, which get a Sync acknowledging GSR, instead of (as usual) P.seqno. This can lead to an oscillating ping-pong flood of Reset packets. In fact, it has been observed on the wire as follows: 1. client establishes connection to server; 2. before server can write to client, client crashes without notifying the server (NB: now no longer possible due to ABORT function); 3. server sends DCCP-Data packet (has no ackno); 4. client generates Reset "No Connection", seqno=0, increments seqno; 5. server replies with Sync, using ackno = P.seqno; 6. client generates Reset "No Connection" with seqno = ackno + 1; 7. goto (5). The difference is that now in (5) the server uses GSR. This causes the Reset sent by the client in (6) to become sequence-valid, so that in (7) the vicious circle is broken; the Reset is then enqueued and causes the socket to enter TIMEWAIT state. Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk> Signed-off-by: Ian McDonald <ian.mcdonald@jandi.co.nz> Signed-off-by: Arnaldo Carvalho de Melo <acme@ghostprotocols.net> Signed-off-by: David S. Miller <davem@davemloft.net>
2007-10-10[DCCP]: Shorten variable names in dccp_check_seqnoGerrit Renker1-23/+17
This patch is in part required by the next patch; it * replaces 6 instances of `DCCP_SKB_CB(skb)->dccpd_seq' with `seqno'; * replaces 7 instances of `DCCP_SKB_CB(skb)->dccpd_ack_seq' with `ackno'; * replaces 1 use of dccp_inc_seqno() by unfolding `ADD48' macro in place. No changes in algorithm, all changes are text replacement/substitution. Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk> Signed-off-by: Ian McDonald <ian.mcdonald@jandi.co.nz> Signed-off-by: Arnaldo Carvalho de Melo <acme@ghostprotocols.net> Signed-off-by: David S. Miller <davem@davemloft.net>
2007-10-10[DCCP]: Simplify interface of dccp_sample_rttGerrit Renker3-34/+19
The third parameter of dccp_sample_rtt now becomes useless and is removed. Also combined the subtraction of the timestamp echo and the elapsed time. This is safe, since (a) presence of timestamp echo is tested first and (b) elapsed time is either present and non-zero or it is not set and equals 0 due to the memset in dccp_parse_options. To avoid measuring option-processing time, the timestamp for measuring the initial Request/Response RTT sample is taken directly when the function is called (the Linux implementation always adds a timestamp on the Request, so there is no loss in doing this). Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk> Signed-off-by: Ian McDonald <ian.mcdonald@jandi.co.nz> Signed-off-by: Arnaldo Carvalho de Melo <acme@ghostprotocols.net> Signed-off-by: David S. Miller <davem@davemloft.net>
2007-10-10[DCCP]: Provide 10s of microsecond timesourceGerrit Renker4-1/+26
This provides a timesource, conveniently used for DCCP timestamps, which returns the elapsed time in 10s of microseconds since initialisation. This makes for a wrap-around time of about 11.9 hours, which should be sufficient for most applications. Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk> Signed-off-by: Arnaldo Carvalho de Melo <acme@ghostprotocols.net> Signed-off-by: David S. Miller <davem@davemloft.net>
2007-10-10[DCCP]: Reuse ktime_get_real() calls againGerrit Renker1-23/+16
This patch reduces the number of timestamps taken in the receive path for each packet. The ccid3_hc_tx_update_x() routine is called in * the receive path for each CCID3-controlled packet * for the nofeedback timer (if no feedback arrives during 4 RTT) Currently, when there is no loss, each packet gets timestamped twice. The patch resolves this by recycling the first timestamp taken on packet reception for RTT sampling. When the no_feedback_timer() is called, then the timestamp argument is simply set to NULL - so that ccid3_hc_tx_update_x() takes care of the logic. Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk> Signed-off-by: Arnaldo Carvalho de Melo <acme@ghostprotocols.net> Signed-off-by: David S. Miller <davem@davemloft.net>
2007-10-10[MAC80211]: rename ieee80211_cfg.h to cfg.hMichael Wu3-5/+5
Might as well rename ieee80211_cfg.h to cfg.h to keep things consistent. Signed-off-by: Michael Wu <flamingice@sourmilk.net> Signed-off-by: John W. Linville <linville@tuxdriver.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2007-10-10[MAC80211]: kill vlan_idJohannes Berg2-3/+0
Each station has a vlan_id that is useless. Remove it. Signed-off-by: Johannes Berg <johannes@sipsolutions.net> Signed-off-by: Michael Wu <flamingice@sourmilk.net> Signed-off-by: John W. Linville <linville@tuxdriver.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2007-10-10[MAC80211]: kill IE parse typedefJohannes Berg1-4/+3
The parse result typedef isn't needed. Signed-off-by: Johannes Berg <johannes@sipsolutions.net> Signed-off-by: Michael Wu <flamingice@sourmilk.net> Signed-off-by: John W. Linville <linville@tuxdriver.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2007-10-10[MAC80211]: rename ieee80211_cfg.c to cfg.cJohannes Berg2-1/+1
It's just painful to have the extra ieee80211_ prefix. Signed-off-by: Johannes Berg <johannes@sipsolutions.net> Signed-off-by: Michael Wu <flamingice@sourmilk.net> Signed-off-by: John W. Linville <linville@tuxdriver.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2007-10-10[MAC80211]: print out wiphy name instead of master deviceJohannes Berg6-17/+19
This makes mac80211 print out the wiphy name instead of the master device name where appropriate. Signed-off-by: Johannes Berg <johannes@sipsolutions.net> Signed-off-by: Michael Wu <flamingice@sourmilk.net> Signed-off-by: John W. Linville <linville@tuxdriver.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2007-10-10[MAC80211]: remove tx info sw_retry_attempt memberJohannes Berg1-3/+0
This is unused. Signed-off-by: Johannes Berg <johannes@sipsolutions.net> Signed-off-by: Michael Wu <flamingice@sourmilk.net> Signed-off-by: John W. Linville <linville@tuxdriver.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2007-10-10[MAC80211]: fix warnings introduced by the doc patchesJohannes Berg1-0/+6
This fixes a warning about NUM_IEEE80211_MODES missing in a switch statement. Intentionally do not add a default case so we get warnings at these places if we need to add new modes. Signed-off-by: Johannes Berg <johannes@sipsolutions.net> Signed-off-by: Michael Wu <flamingice@sourmilk.net> Signed-off-by: John W. Linville <linville@tuxdriver.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2007-10-10[MAC80211]: yet more documentationJohannes Berg1-49/+149
Add more mac80211 documentation. Signed-off-by: Johannes Berg <johannes@sipsolutions.net> Signed-off-by: Michael Wu <flamingice@sourmilk.net> Signed-off-by: John W. Linville <linville@tuxdriver.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2007-10-10[MAC80211]: remove IEEE80211_CONF_SSID_HIDDENJohannes Berg1-2/+1
The IEEE80211_CONF_SSID_HIDDEN setting is not useful for any driver we have and should be a per-interface setting anyway. Remove it. Signed-off-by: Johannes Berg <johannes@sipsolutions.net> Signed-off-by: Michael Wu <flamingice@sourmilk.net> Signed-off-by: John W. Linville <linville@tuxdriver.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2007-10-10[MAC80211]: remove key threshold stuffJohannes Berg8-68/+3
This patch removes the key threshold stuff from mac80211. I have patches for later that add it as a per-key setting to nl/cfg80211. Signed-off-by: Johannes Berg <johannes@sipsolutions.net> Signed-off-by: Michael Wu <flamingice@sourmilk.net> Signed-off-by: John W. Linville <linville@tuxdriver.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2007-10-10[MAC80211]: allow drivers to indicate failed FCS/PLCP checksumJohannes Berg2-3/+35
This patch allows drivers to indicate bad FCS/PLCP CRC to the stack and have the stack drop packets like that except for monitor interfaces. Signed-off-by: Johannes Berg <johannes@sipsolutions.net> Signed-off-by: Michael Wu <flamingice@sourmilk.net> Signed-off-by: John W. Linville <linville@tuxdriver.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2007-10-10[LIBERTAS]: fix oops on the blackfin architectureVladimir Davydov1-3/+5
Fixing memory alignment problems on the blackfin architecture (maybe on the ARM also) Signed-off-by: Vladimir Davydov <vladimir.davydov@promwad.com> Signed-off-by: John W. Linville <linville@tuxdriver.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2007-10-10[LIBERTAS]: fix oops on the blackfin architectureVladimir Davydov1-2/+4
Reserve two bytes to align pointer to the IP header. Signed-off-by: Vladimir Davydov <vladimir.davydov@promwad.com> Signed-off-by: John W. Linville <linville@tuxdriver.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2007-10-10[LIBERTAS]: fix interrupts in CF driverRyan Mallon1-14/+19
The following patch fixes the tx transmit timeout problem, which is caused by the interrupts being incorrectly check and masked. The patch moves the interrupt masking code so that interrupts are enabled only when the driver is registered and only disabled when the driver is unregistered. Signed-off-by: Ryan Mallon <ryan@bluewatersys.com> Signed-off-by: John W. Linville <linville@tuxdriver.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2007-10-10[LIBERTAS]: set dnld_sent correctly for CF partsRyan Mallon1-1/+2
Corrects a minor bug with priv->dnld_sent being set incorrectly in if_cs_host_to_card. Signed-off-by: Ryan Mallon <ryan@bluewatersys.com> Signed-off-by: John W. Linville <linville@tuxdriver.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2007-10-10[B43LEGACY]: Change the hardware radio enable logic and cleanup codeLarry Finger4-34/+25
This change cleans up the radio-related messages in several ways. (1) The state of the rfkill switch is assumed to be on, rather than tested. Now, any user without such a switch will not see any messages. For devices with such a switch, a message will be logged only if the initial state is off, or if the switch is toggled. (2) The routine for testing the switch state is no longer inline. (3) The LED handling routine is simplified. (4) The "Radio turned off" message that has confused some users has been changed to "Radio initialized". This patch is patterned after a similar change to b43 by Michael Buesch. Signed-off-by: Larry Finger <Larry.Finger@lwfinger.net> Signed-off-by: John W. Linville <linville@tuxdriver.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2007-10-10[B43LEGACY]: Support for turning the radio off from software.Larry Finger4-19/+61
This adds support for turning the radio off in software. That's useful in environments, where you don't want the RF to radiate any signals, but don't want to bring the interface down. This patch is based on a similar patch of b43 by Michael Buesch. Signed-off-by: Larry Finger <larry.finger@lwfinger.net> Signed-off-by: John W. Linville <linville@tuxdriver.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2007-10-10[B43]: Support for turning the radio off from software.Michael Buesch3-13/+63
This adds support for turning the radio off in software. That's useful in environments, where you don't want the RF to radiate any signals, but don't want to bring the interface down. Cc: Larry Finger <larry.finger@lwfinger.net> Signed-off-by: Michael Buesch <mb@bu3sch.de> Signed-off-by: John W. Linville <linville@tuxdriver.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2007-10-10[B43]: Remove the "radio hw enabled" message on startup.Michael Buesch1-3/+3
This message is useless. Only report state changes. Cc: Larry Finger <larry.finger@lwfinger.net> Signed-off-by: Michael Buesch <mb@bu3sch.de> Signed-off-by: John W. Linville <linville@tuxdriver.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2007-10-10[MAC80211]: Add support for setting TX power and radio statusMichael Buesch2-2/+39
This adds support for disabling the radio and setting the TXpower through wext. This also fixes the prism TXpower ioctl (It always overwrote the TXpower value in ieee80211_hw_config()) Signed-off-by: Michael Buesch <mb@bu3sch.de> Signed-off-by: John W. Linville <linville@tuxdriver.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2007-10-10[IEEE80211]: Fix softmac lockdep reports.Johannes Berg7-17/+25
It seems I was actually able to hit this deadlock, on my quad G5 softmac locks up more often than not. This fixes it by using an own workqueue that can safely be flushed under RTNL. Not sure if the patch is correct with the workqueue naming. And don't think with the patch it doesn't continually lock up. It still does, just doesn't invoke lockdep warnings all the time. Signed-off-by: Johannes Berg <johannes@sipsolutions.net> Signed-off-by: John W. Linville <linville@tuxdriver.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2007-10-10[B43]: Change loglevel of radio-enable message.Michael Buesch3-29/+26
Also cleanup the code a bit and remove the inline. Signed-off-by: Michael Buesch <mb@bu3sch.de> Signed-off-by: John W. Linville <linville@tuxdriver.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2007-10-10[SSB]: Sparse fixes.Michael Buesch3-9/+10
This fixes all Sparse warnings in SSB. No semantics change. Signed-off-by: Michael Buesch <mb@bu3sch.de> Signed-off-by: John W. Linville <linville@tuxdriver.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2007-10-10[SSB]: Use ioreadX() and iowriteX() for PCI.Michael Buesch1-4/+4
On a PCI bus use ioreadX() and iowriteX(). We map the I/O space with pci_iomap(), so we must use the correct accessor functions, too. readX() and writeX() are not guaranteed to accept the cookie returned from pci_iomap() (though, it currently works on most architectures). Signed-off-by: Michael Buesch <mb@bu3sch.de> Signed-off-by: John W. Linville <linville@tuxdriver.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2007-10-10[B43]: Don't lock irq_lock in debugfs txpower adjustMichael Buesch1-14/+5
It's not required and the txpower adjustment must not be in atomic. Signed-off-by: Michael Buesch <mb@bu3sch.de> Signed-off-by: John W. Linville <linville@tuxdriver.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2007-10-10[P54PCI]: terminate pci tableAndrew Morton1-0/+1
Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: John W. Linville <linville@tuxdriver.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2007-10-10[ZD1211RD]: add USB id for Telegent TG54USB WLAN adapterUlrich Kunitz1-0/+1
Reinhard Speyerer reported at 2007-08-10 a new device. Here are the information strings. Product: Telegent TG54USB WLAN Adapter USB ID: 129b:1666 Chip ID: zd1211 chip 129b:1666 v4330 high 00-01-36 RF2959_RF pa0 ----- FCC ID: N89-UW620Z Signed-off-by: Ulrich Kunitz <kune@deine-taler.de> Signed-off-by: Daniel Drake <dsd@gentoo.org> Signed-off-by: John W. Linville <linville@tuxdriver.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2007-10-10[BCM43XX]: Change radio hardware switch status printk from debug to regularLarry Finger2-3/+3
Some distros ship bcm43xx with debugging printout disabled. For those BCM43xx devices with radio on/off switches, this makes it impossible to know if the radio is on or off. This patch changes a pair of debug printk's into ordinary printk's. It also changes the message that prints when the radio is initialized to the off state as the old message seems to confuse users. Signed-off-by: Larry Finger <Larry.Finger@lwfinger.net> Signed-off-by: John W. Linville <linville@tuxdriver.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2007-10-10[ZD1211RW]: Don't needlessly initialize variable to NULL in zd_chipJesper Juhl1-1/+1
No need to initialize to NULL when variable is never used before it's assigned the return value of a kmalloc() call. Signed-off-by: Jesper Juhl <jesper.juhl@gmail.com> Signed-off-by: John W. Linville <linville@tuxdriver.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2007-10-10[NET]: note that NETIF_F_LLTX is deprecatedChristian Borntraeger2-2/+4
Am Freitag, 21. September 2007 schrieb Herbert Xu: > Please don't use LLTX in new drivers. We're trying to get rid > of it since it's > > 1) unnecessary; > 2) causes problems with AF_PACKET seeing things twice. I suggest to document that LLTX is deprecated. Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com> Acked-by: Herbert Xu <herbert@gondor.apana.org.au> Signed-off-by: David S. Miller <davem@davemloft.net>
2007-10-10[IWLWIFI]: remove per-file CFLAGS for IWL defineZhu Yi7-6/+12
Signed-off-by: Zhu Yi <yi.zhu@intel.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2007-10-10[NET_SCHED]: explict hold dev tx lockJamal Hadi Salim1-17/+2
For N cpus, with full throttle traffic on all N CPUs, funneling traffic to the same ethernet device, the devices queue lock is contended by all N CPUs constantly. The TX lock is only contended by a max of 2 CPUS. In the current mode of operation, after all the work of entering the dequeue region, we may endup aborting the path if we are unable to get the tx lock and go back to contend for the queue lock. As N goes up, this gets worse. The changes in this patch result in a small increase in performance with a 4CPU (2xdual-core) with no irq binding. Both e1000 and tg3 showed similar behavior; Signed-off-by: Jamal Hadi Salim <hadi@cyberus.ca> Signed-off-by: David S. Miller <davem@davemloft.net>
2007-10-10[NET]: Dynamically allocate the loopback device, part 2.Daniel Lezcano1-28/+44
Doing this makes loopback.c a better example of how to do a simple network device, and it removes the special case single static allocation of a struct net_device, hopefully making maintenance easier. Signed-off-by: Eric W. Biederman <ebiederm@xmission.com> Signed-off-by: Daniel Lezcano <dlezcano@fr.ibm.com> Acked-By: Kirill Korotaev <dev@sw.ru> Acked-by: Benjamin Thery <benjamin.thery@bull.net>
2007-10-10[NET]: Dynamically allocate the loopback device, part 1.Daniel Lezcano16-53/+55
This patch replaces all occurences to the static variable loopback_dev to a pointer loopback_dev. That provides the mindless, trivial, uninteressting change part for the dynamic allocation for the loopback. Signed-off-by: Eric W. Biederman <ebiederm@xmission.com> Signed-off-by: Daniel Lezcano <dlezcano@fr.ibm.com> Acked-By: Kirill Korotaev <dev@sw.ru> Acked-by: Benjamin Thery <benjamin.thery@bull.net> Signed-off-by: David S. Miller <davem@davemloft.net>
2007-10-10[NL80211]: add netlink interface to cfg80211Johannes Berg10-9/+762
Signed-off-by: Johannes Berg <johannes@sipsolutions.net> Signed-off-by: John W. Linville <linville@tuxdriver.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2007-10-10[TCP]: Minor coding style fixup.David S. Miller1-2/+4
Signed-off-by: David S. Miller <davem@davemloft.net>
2007-10-10[TCP]: Avoid clearing sacktag hint in trivial situationsIlpo Järvinen3-11/+21
There's no reason to clear the sacktag skb hint when small part of the rexmit queue changes. Account changes (if any) instead when fragmenting/collapsing. RTO/FRTO do not touch SACKED_ACKED bits so no need to discard SACK tag hint at all. Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi> Signed-off-by: David S. Miller <davem@davemloft.net>
2007-10-10[TCP]: Enable SACK enhanced FRTO (RFC4138) by defaultIlpo Järvinen1-1/+1
Most of the description that follows comes from my mail to netdev (some editing done): Main obstacle to FRTO use is its deployment as it has to be on the sender side where as wireless link is often the receiver's access link. Take initiative on behalf of unlucky receivers and enable it by default in future Linux TCP senders. Also IETF seems to interested in advancing FRTO from experimental [1]. How does FRTO help? =================== FRTO detects spurious RTOs and avoids a number of unnecessary retransmissions and a couple of other problems that can arise due to incorrect guess made at RTO (i.e., that segments were lost when they actually got delayed which is likely to occur e.g. in wireless environments with link-layer retransmission). Though FRTO cannot prevent the first (potentially unnecessary) retransmission at RTO, I suspect that it won't cost that much even if you have to pay for each bit (won't be that high percentage out of all packets after all :-)). However, usually when you have a spurious RTO, not only the first segment unnecessarily retransmitted but the *whole window*. It goes like this: all cumulative ACKs got delayed due to in-order delivery, then TCP will actually send 1.5*original cwnd worth of data in the RTO's slow-start when the delayed ACKs arrive (basically the original cwnd worth of it unnecessarily). In case one is interested in minimizing unnecessary retransmissions e.g. due to cost, those rexmissions must never see daylight. Besides, in the worst case the generated burst overloads the bottleneck buffers which is likely to significantly delay the further progress of the flow. In case of ll rexmissions, ACK compression often occurs at the same time making the burst very "sharp edged" (in that case TCP often loses most of the segments above high_seq => very bad performance too). When FRTO is enabled, those unnecessary retransmissions are fully avoided except for the first segment and the cwnd behavior after detected spurious RTO is determined by the response (one can tune that by sysctl). Basic version (non-SACK enhanced one), FRTO can fail to detect spurious RTO as spurious and falls back to conservative behavior. ACK lossage is much less significant than reordering, usually the FRTO can detect spurious RTO if at least 2 cumulative ACKs from original window are preserved (excluding the ACK that advances to high_seq). With SACK-enhanced version, the detection is quite robust. FRTO should remove the need to set a high lower bound for the RTO estimator due to delay spikes that occur relatively common in some environments (esp. in wireless/cellular ones). [1] http://www1.ietf.org/mail-archive/web/tcpm/current/msg02862.html Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi> Signed-off-by: David S. Miller <davem@davemloft.net>
2007-10-10[TCP] FRTO: Update sysctl documentationIlpo Järvinen1-5/+12
Since the SACK enhanced FRTO was added, the code has been under test numerous times so remove "experimental" claim from the documentation. Also be a bit more verbose about the usage. Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi> Signed-off-by: David S. Miller <davem@davemloft.net>