From 615e3cc84cf25f501c65cc91f9eb31b4d7b2b35a Mon Sep 17 00:00:00 2001 From: hidnplayr Date: Sun, 19 Aug 2012 11:21:20 +0000 Subject: [PATCH] Some updates for TCP git-svn-id: svn://kolibrios.org@2930 a494cfbc-eb01-0410-851d-a64ba20cac60 --- kernel/branches/net/network/tcp_input.inc | 667 ++++++++++------------ kernel/branches/net/network/tcp_subr.inc | 12 +- 2 files changed, 302 insertions(+), 377 deletions(-) diff --git a/kernel/branches/net/network/tcp_input.inc b/kernel/branches/net/network/tcp_input.inc index 5a756a1e69..24bcdba836 100644 --- a/kernel/branches/net/network/tcp_input.inc +++ b/kernel/branches/net/network/tcp_input.inc @@ -36,7 +36,13 @@ TCP_input: DEBUGF 1,"TCP_input: size=%u\n", ecx -; First, re-calculate the checksum +; First, record the current time + mov eax, [timer_ticks] + mov [esp+4], eax + +; then, re-calculate the checksum (if not already done by hw) +; test [ebx + NET_DEVICE.hwacc], HWACC_TCP_IPv4_IN +; jnz .checksum_ok push ecx esi pushw [esi + TCP_header.Checksum] @@ -46,9 +52,9 @@ TCP_input: cmp cx, dx pop edx ecx jne .drop_no_socket + .checksum_ok: - DEBUGF 1,"TCP_input: Checksum ok\n" - +; Verify the data offset and [edx + TCP_header.DataOffset], 0xf0 ; Calculate TCP segment header size (throwing away unused reserved bits in TCP header) shr [edx + TCP_header.DataOffset], 2 cmp [edx + TCP_header.DataOffset], sizeof.TCP_header ; Now see if it's at least the size of a standard TCP header @@ -59,30 +65,6 @@ TCP_input: jb .drop_no_socket ; If total segment size is less then the advertised header size, drop packet DEBUGF 1,"TCP_input: %u bytes of data\n", ecx -;----------------------------------------------------------------------------------------- -; Check if this packet has a timestamp option (We do it here so we can process it quickly) - - cmp eax, sizeof.TCP_header + 12 ; Timestamp option is 12 bytes - jb .no_timestamp - je .is_ok - - cmp byte [edx + sizeof.TCP_header + 12], TCP_OPT_EOL ; end of option list - jne .no_timestamp - - .is_ok: - test [edx + TCP_header.Flags], TH_SYN ; SYN flag must not be set - jnz .no_timestamp - - cmp dword [edx + sizeof.TCP_header], 0x0101080a ; Timestamp header - jne .no_timestamp - - DEBUGF 1,"TCP_input: timestamp ok\n" - - ; TODO: Parse the option - ; TODO: Set a Bit in the TCP to tell all options are parsed - - .no_timestamp: - ;------------------------------------------- ; Convert Big-endian values to little endian @@ -94,8 +76,8 @@ TCP_input: ntohw [edx + TCP_header.SourcePort] ntohw [edx + TCP_header.DestinationPort] -;------------------------------------------------------------ -; Next thing to do is find the TCPS (thus, the socket pointer) +;------------------------ +; Find the socket pointer ; IP Packet TCP Destination Port = local Port ; (IP Packet SenderAddress = Remote IP) OR (Remote IP = 0) @@ -133,7 +115,9 @@ TCP_input: .found_socket: ; ebx now contains the socketpointer DEBUGF 1,"TCP_input: socket ptr=%x state=%u flags=%x\n", ebx, [ebx + TCP_SOCKET.t_state], [edx + TCP_header.Flags]:2 +;------------- ; update stats + inc [TCP_segments_rx] ; FIXME: correct interface? ;---------------------------- @@ -170,38 +154,11 @@ TCP_input: mov dword [edx + TCP_header.Window], eax ; word after window is checksum, we dont need checksum anymore pop ecx -;----------------------------------- -; Is this socket a listening socket? +;--------------------------------------- +; Are we accepting incoming connections? test [ebx + SOCKET.options], SO_ACCEPTCON - jz .no_listening_socket - - DEBUGF 1,"TCP_input: Accepting new connection\n" - - pusha - lea ecx, [ebx + SOCKET.mutex] - call mutex_unlock - popa - - push ecx edx esi edi ;;; - call SOCKET_fork - pop edi esi edx ecx - - test eax, eax - jz .drop - - push dword [edi + 4] ; Ipv4 destination addres - pop [eax + IP_SOCKET.LocalIP] - - push [edx + TCP_header.DestinationPort] - pop [eax + TCP_SOCKET.LocalPort] - - mov [eax + TCP_SOCKET.t_state], TCPS_LISTEN - mov ebx, eax - - jmp .LISTEN - - .no_listening_socket: + jnz .accept_connection ;------------------------------------- ; Reset idle timer and keepalive timer @@ -246,7 +203,7 @@ TCP_input: jmp .no_options ; If we reach here, some unknown options were received, skip them all! .opt_nop: - inc edi + inc esi jmp .opt_loop .opt_maxseg: @@ -263,7 +220,7 @@ TCP_input: mov [ebx + TCP_SOCKET.t_maxseg], eax @@: - add edi, 4 + add esi, 4 jmp .opt_loop @@ -278,17 +235,21 @@ TCP_input: ;;;;; @@: - add edi, 3 + add esi, 3 jmp .opt_loop .opt_timestamp: - cmp byte [esi+1], 10 + cmp byte [esi+1], 10 ; length must be 10 jne .no_options DEBUGF 1,"TCP_input: Got timestamp option\n" - ;;;;; + push dword [esi + 2] ; timestamp + pop [ebx + TCP_SOCKET.ts_recent] + + push dword [esi + 6] ; timestamp echo reply + pop [ebx + TCP_SOCKET.ts_ecr] add esi, 10 jmp .opt_loop @@ -360,10 +321,6 @@ TCP_input: ;--------------------------------- ; Packet is a pure ACK, process it -; Update RTT estimators - -;;; TODO - ; Delete acknowledged bytes from send buffer pusha mov ecx, eax @@ -371,6 +328,19 @@ TCP_input: call SOCKET_ring_free popa +; Update RTT estimators + +; if ts_present +; mov eax, [esp + 4] ; timestamp when this segment was received +; sub eax, [ebx + TCP_SOCKET.ts_ecr] +; inc eax +; call TCP_xmit_timer + +; else if (t_rtt && SEG_GT(ti_ack - t_rtsec)) +; mov eax, [ebx + t_rtt] +; call TCP_xmit_timer +; end if + ; update window pointers mov eax, [edx + TCP_header.AckNumber] mov [ebx + TCP_SOCKET.SND_UNA], eax @@ -407,7 +377,7 @@ TCP_input: ;;; TODO - jnz .not_uni_xfer +; jnz .not_uni_xfer ; Complete processing of received data @@ -457,188 +427,6 @@ TCP_input: cmp [ebx + TCP_SOCKET.t_state], TCPS_SYN_SENT je .SYN_SENT - jmp .NOT_LISTEN_OR_SYN_SENT - - - -;------------- -; Passive Open - -align 4 - .LISTEN: - - DEBUGF 1,"TCP_input: state=listen\n" - - test [edx + TCP_header.Flags], TH_RST ;;; TODO: kill new socket on error - jnz .drop - - test [edx + TCP_header.Flags], TH_ACK - jnz .drop_with_reset - - test [edx + TCP_header.Flags], TH_SYN - jz .drop - -;;; TODO: check if it's a broadcast or multicast, and drop if so - - push dword [edi] ; Ipv4 source addres - pop [ebx + IP_SOCKET.RemoteIP] - - push [edx + TCP_header.SourcePort] - pop [ebx + TCP_SOCKET.RemotePort] - - push [edx + TCP_header.SequenceNumber] - pop [ebx + TCP_SOCKET.IRS] - - mov eax, [TCP_sequence_num] - add [TCP_sequence_num], 64000 / 2 - mov [ebx + TCP_SOCKET.ISS], eax - mov [ebx + TCP_SOCKET.SND_NXT], eax - - TCP_sendseqinit ebx - TCP_rcvseqinit ebx - - mov [ebx + TCP_SOCKET.t_state], TCPS_SYN_RECEIVED - mov [ebx + TCP_SOCKET.t_flags], TF_ACKNOW - mov [ebx + TCP_SOCKET.timer_keepalive], TCP_time_keep_interval ;;;; macro - - lea eax, [ebx + STREAM_SOCKET.snd] - call SOCKET_ring_create - - lea eax, [ebx + STREAM_SOCKET.rcv] - call SOCKET_ring_create - -;;; call SOCKET_notify_owner - - jmp .trim_then_step6 - - - - - - - - - - -;------------ -; Active Open - -align 4 -.SYN_SENT: - - DEBUGF 1,"TCP_input: state=syn_sent\n" - - test [edx + TCP_header.Flags], TH_ACK - jz @f - - mov eax, [edx + TCP_header.AckNumber] - cmp eax, [ebx + TCP_SOCKET.ISS] - jbe .drop_with_reset - - cmp eax, [ebx + TCP_SOCKET.SND_MAX] - ja .drop_with_reset - @@: - - test [edx + TCP_header.Flags], TH_RST - jz @f - - test [edx + TCP_header.Flags], TH_ACK - jz .drop - - mov eax, ebx - mov ebx, ECONNREFUSED - call TCP_drop - - jmp .drop - @@: - - test [edx + TCP_header.Flags], TH_SYN - jz .drop - -; at this point, segment seems to be valid - - test [edx + TCP_header.Flags], TH_ACK - jz .no_syn_ack - -; now, process received SYN in response to an active open - - mov eax, [edx + TCP_header.AckNumber] - mov [ebx + TCP_SOCKET.SND_UNA], eax - cmp eax, [ebx + TCP_SOCKET.SND_NXT] - jbe @f - mov [ebx + TCP_SOCKET.SND_NXT], eax - @@: - - .no_syn_ack: - - mov [ebx + TCP_SOCKET.timer_retransmission], 0 ; disable retransmission - - push [edx + TCP_header.SequenceNumber] - pop [ebx + TCP_SOCKET.IRS] - - TCP_rcvseqinit ebx - - or [ebx + TCP_SOCKET.t_flags], TF_ACKNOW - - mov eax, [ebx + TCP_SOCKET.SND_UNA] - cmp eax, [ebx + TCP_SOCKET.ISS] - jbe .simultaneous_open - - test [edx + TCP_header.Flags], TH_ACK - jz .simultaneous_open - - DEBUGF 1,"TCP_input: active open\n" - -;;; TODO: update stats - -; set socket state to connected - mov [ebx + SOCKET.state], SS_ISCONNECTED - mov [ebx + TCP_SOCKET.t_state], TCPS_ESTABLISHED - -;;; TODO: check if we should scale the connection (567-572) - mov [ebx + TCP_SOCKET.SND_SCALE], 0 - -;;; TODO: update RTT estimators - - jmp .trim_then_step6 - - .simultaneous_open: - - DEBUGF 1,"TCP_input: simultaneous open\n" -; We have received a syn but no ACK, so we are having a simultaneous open.. - mov [ebx + TCP_SOCKET.t_state], TCPS_SYN_RECEIVED - - - - - - - -;------------------------------------- -; Common processing for receipt of SYN - - .trim_then_step6: - - inc [edx + TCP_header.SequenceNumber] - -;;; TODO: Drop any received data that follows receive window (590) - - mov eax, [edx + TCP_header.SequenceNumber] - mov [ebx + TCP_SOCKET.RCV_UP], eax - dec eax - mov [ebx + TCP_SOCKET.SND_WL1], eax - - jmp .ack_processed - - - - - - - - - .NOT_LISTEN_OR_SYN_SENT: - DEBUGF 1,"TCP_input: state is not listen or syn_sent\n" ;-------------------------------------------- @@ -729,7 +517,6 @@ align 4 cmp [edx + TCP_header.Flags], TH_ACK jz .drop_after_ack - .duplicate: DEBUGF 1,"TCP_input: Duplicate received\n" @@ -740,7 +527,6 @@ align 4 ;;; TODO jmp .drop_after_ack - .no_duplicate: ;----------------------------------------------- @@ -857,7 +643,6 @@ align 4 .no_rst: - ;-------------------------------------- ; handle SYN-full and ACK-less segments @@ -1163,7 +948,6 @@ align 4 mov [ebx + TCP_SOCKET.t_state], TCPS_FIN_WAIT_2 jmp .ack_processed - .ack_c: jnc .ack_processed @@ -1175,25 +959,213 @@ align 4 call SOCKET_is_disconnected jmp .ack_processed - .ack_la: jnc .ack_processed - mov eax, ebx call TCP_disconnect jmp .drop - .ack_tw: mov [ebx + TCP_SOCKET.timer_timed_wait], 2 * TCP_time_MSL jmp .drop_after_ack - - .reset_dupacks: ; We got a new ACK, reset duplicate ACK counter - mov [ebx + TCP_SOCKET.t_dupacks], 0 + jmp .ack_processed + + + +;------------- +; Passive Open + +align 4 + + .accept_connection: + + DEBUGF 1,"TCP_input: Accepting new connection\n" + + pusha + lea ecx, [ebx + SOCKET.mutex] + call mutex_unlock + popa + + push ecx edx esi edi ;;; + call SOCKET_fork + pop edi esi edx ecx + + test eax, eax + jz .drop + + push dword [edi + 4] ; Ipv4 destination addres + pop [eax + IP_SOCKET.LocalIP] + + push [edx + TCP_header.DestinationPort] + pop [eax + TCP_SOCKET.LocalPort] + + mov [eax + TCP_SOCKET.t_state], TCPS_LISTEN + mov ebx, eax + + .LISTEN: + + DEBUGF 1,"TCP_input: state=listen\n" + + test [edx + TCP_header.Flags], TH_RST ;;; TODO: kill new socket on error + jnz .drop + + test [edx + TCP_header.Flags], TH_ACK + jnz .drop_with_reset + + test [edx + TCP_header.Flags], TH_SYN + jz .drop + +;;; TODO: check if it's a broadcast or multicast, and drop if so + + push dword [edi] ; Ipv4 source addres + pop [ebx + IP_SOCKET.RemoteIP] + + push [edx + TCP_header.SourcePort] + pop [ebx + TCP_SOCKET.RemotePort] + + push [edx + TCP_header.SequenceNumber] + pop [ebx + TCP_SOCKET.IRS] + + mov eax, [TCP_sequence_num] + add [TCP_sequence_num], 64000 / 2 + mov [ebx + TCP_SOCKET.ISS], eax + mov [ebx + TCP_SOCKET.SND_NXT], eax + + TCP_sendseqinit ebx + TCP_rcvseqinit ebx + + mov [ebx + TCP_SOCKET.t_state], TCPS_SYN_RECEIVED + mov [ebx + TCP_SOCKET.t_flags], TF_ACKNOW + mov [ebx + TCP_SOCKET.timer_keepalive], TCP_time_keep_interval ;;;; macro + + lea eax, [ebx + STREAM_SOCKET.snd] + call SOCKET_ring_create + + lea eax, [ebx + STREAM_SOCKET.rcv] + call SOCKET_ring_create + +;;; call SOCKET_notify_owner + + jmp .trim_then_step6 + + + + + + + + + + +;------------ +; Active Open + +align 4 +.SYN_SENT: + + DEBUGF 1,"TCP_input: state=syn_sent\n" + + test [edx + TCP_header.Flags], TH_ACK + jz @f + + mov eax, [edx + TCP_header.AckNumber] + cmp eax, [ebx + TCP_SOCKET.ISS] + jbe .drop_with_reset + + cmp eax, [ebx + TCP_SOCKET.SND_MAX] + ja .drop_with_reset + @@: + + test [edx + TCP_header.Flags], TH_RST + jz @f + + test [edx + TCP_header.Flags], TH_ACK + jz .drop + + mov eax, ebx + mov ebx, ECONNREFUSED + call TCP_drop + + jmp .drop + @@: + + test [edx + TCP_header.Flags], TH_SYN + jz .drop + +; at this point, segment seems to be valid + + test [edx + TCP_header.Flags], TH_ACK + jz .no_syn_ack + +; now, process received SYN in response to an active open + + mov eax, [edx + TCP_header.AckNumber] + mov [ebx + TCP_SOCKET.SND_UNA], eax + cmp eax, [ebx + TCP_SOCKET.SND_NXT] + jbe @f + mov [ebx + TCP_SOCKET.SND_NXT], eax + @@: + + .no_syn_ack: + + mov [ebx + TCP_SOCKET.timer_retransmission], 0 ; disable retransmission + + push [edx + TCP_header.SequenceNumber] + pop [ebx + TCP_SOCKET.IRS] + + TCP_rcvseqinit ebx + + or [ebx + TCP_SOCKET.t_flags], TF_ACKNOW + + mov eax, [ebx + TCP_SOCKET.SND_UNA] + cmp eax, [ebx + TCP_SOCKET.ISS] + jbe .simultaneous_open + + test [edx + TCP_header.Flags], TH_ACK + jz .simultaneous_open + + DEBUGF 1,"TCP_input: active open\n" + +;;; TODO: update stats + +; set socket state to connected + mov [ebx + SOCKET.state], SS_ISCONNECTED + mov [ebx + TCP_SOCKET.t_state], TCPS_ESTABLISHED + +;;; TODO: check if we should scale the connection (567-572) + mov [ebx + TCP_SOCKET.SND_SCALE], 0 + +;;; TODO: update RTT estimators + + jmp .trim_then_step6 + + .simultaneous_open: + + DEBUGF 1,"TCP_input: simultaneous open\n" +; We have received a syn but no ACK, so we are having a simultaneous open.. + mov [ebx + TCP_SOCKET.t_state], TCPS_SYN_RECEIVED + +;------------------------------------- +; Common processing for receipt of SYN + + .trim_then_step6: + + inc [edx + TCP_header.SequenceNumber] + +;;; TODO: Drop any received data that follows receive window (590) + + mov eax, [edx + TCP_header.SequenceNumber] + mov [ebx + TCP_SOCKET.RCV_UP], eax + dec eax + mov [ebx + TCP_SOCKET.SND_WL1], eax + + jmp .ack_processed + + .ack_processed: ; (step 6) @@ -1306,7 +1278,7 @@ align 4 ; FIN processing test [edx + TCP_header.Flags], TH_FIN - jz .no_fin + jz .final_processing DEBUGF 1,"TCP_input: Processing FIN\n" @@ -1327,27 +1299,27 @@ align 4 jmp dword [eax + .FIN_sw_list] .FIN_sw_list: - dd .no_fin ; TCPS_CLOSED - dd .no_fin ; TCPS_LISTEN - dd .no_fin ; TCPS_SYN_SENT + dd .final_processing ; TCPS_CLOSED + dd .final_processing ; TCPS_LISTEN + dd .final_processing ; TCPS_SYN_SENT dd .fin_syn_est ; TCPS_SYN_RECEIVED dd .fin_syn_est ; TCPS_ESTABLISHED - dd .no_fin ; TCPS_CLOSE_WAIT + dd .final_processing ; TCPS_CLOSE_WAIT dd .fin_wait1 ; TCPS_FIN_WAIT_1 - dd .no_fin ; TCPS_CLOSING - dd .no_fin ; TCPS_LAST_ACK + dd .final_processing ; TCPS_CLOSING + dd .final_processing ; TCPS_LAST_ACK dd .fin_wait2 ; TCPS_FIN_WAIT_2 dd .fin_timed ; TCPS_TIMED_WAIT .fin_syn_est: mov [ebx + TCP_SOCKET.t_state], TCPS_CLOSE_WAIT - jmp .no_fin + jmp .final_processing .fin_wait1: mov [ebx + TCP_SOCKET.t_state], TCPS_CLOSING - jmp .no_fin + jmp .final_processing .fin_wait2: @@ -1356,118 +1328,39 @@ align 4 call TCP_cancel_timers mov [ebx + TCP_SOCKET.timer_timed_wait], 2 * TCP_time_MSL call SOCKET_is_disconnected - jmp .no_fin + jmp .final_processing .fin_timed: mov [ebx + TCP_SOCKET.timer_timed_wait], 2 * TCP_time_MSL - jmp .no_fin - - .no_fin: + jmp .final_processing - - -;----------------- -; Final processing - - .final_processing: - - DEBUGF 1,"TCP_input: Final processing\n" - - cmp [ebx + TCP_SOCKET.sendalot], 0 - jne .need_output - - test [ebx + TCP_SOCKET.t_flags], TF_ACKNOW - jz .dumpit - - DEBUGF 1,"TCP_input: ACK now!\n" - - .need_output: - - pusha - lea ecx, [ebx + SOCKET.mutex] - call mutex_unlock - popa - - push ebx - mov eax, ebx - call TCP_output - pop ebx - - call kernel_free - add esp, 4 - ret - - .dumpit: - - DEBUGF 1,"TCP_input: dumping\n" - - pusha - lea ecx, [ebx + SOCKET.mutex] - call mutex_unlock - popa - - call kernel_free - add esp, 4 - ret - - - - - - - -;------------------------------------------ -; Generate an ACK, droping incoming segment - -align 4 -.drop_after_ack: - + .drop_after_ack: DEBUGF 1,"TCP_input: Drop after ACK\n" - test [edx + TCP_header.Flags], TH_RST - jnz .drop - - and [ebx + TCP_SOCKET.t_flags], TF_ACKNOW - - pusha + push edx ebx lea ecx, [ebx + SOCKET.mutex] call mutex_unlock - popa + pop eax edx - push ebx -; mov cl, TH_ACK -; call TCP_respond_socket - mov eax, ebx - call TCP_output - pop ebx + test [edx + TCP_header.Flags], TH_RST + jnz .dumpit - call kernel_free - add esp, 4 - ret + or [eax + TCP_SOCKET.t_flags], TF_ACKNOW + jmp .need_output - - - - - -;------------------------------------------- -; Generate an RST, dropping incoming segment - -align 4 -.drop_with_reset: - + .drop_with_reset: DEBUGF 1,"TCP_input: Drop with reset\n" - pusha + push ebx edx lea ecx, [ebx + SOCKET.mutex] call mutex_unlock - popa + pop edx ebx test [edx + TCP_header.Flags], TH_RST - jnz .drop + jnz .dumpit ;;; if its a multicast/broadcast, also drop @@ -1476,11 +1369,40 @@ align 4 test [edx + TCP_header.Flags], TH_SYN jnz .respond_syn + jmp .dumpit + +;----------------- +; Final processing + + .final_processing: + DEBUGF 1,"TCP_input: Final processing\n" + + push ebx + lea ecx, [ebx + SOCKET.mutex] + call mutex_unlock + pop eax + + cmp [eax + TCP_SOCKET.sendalot], 0 + jne .need_output + + test [eax + TCP_SOCKET.t_flags], TF_ACKNOW + jz .dumpit + DEBUGF 1,"TCP_input: ACK now!\n" + + .need_output: + call TCP_output + + .dumpit: + DEBUGF 1,"TCP_input: dumping\n" call kernel_free add esp, 4 ret + + + + .respond_ack: push ebx @@ -1505,15 +1427,14 @@ align 4 ;----- ; Drop -align 4 -.drop: + .drop: pusha lea ecx, [ebx + SOCKET.mutex] call mutex_unlock popa -.drop_not_locked: + .drop_not_locked: DEBUGF 1,"TCP_input: Dropping packet\n" @@ -1523,14 +1444,14 @@ align 4 ;;;; kill the newly created socket + .drop_no_socket: + DEBUGF 1,"TCP_input: Drop (no socket)\n" + call kernel_free add esp, 4 ret - - - -.drop_with_reset_no_socket: + .drop_with_reset_no_socket: DEBUGF 1,"TCP_input: Drop with reset (no socket)\n" @@ -1545,13 +1466,7 @@ align 4 test [edx + TCP_header.Flags], TH_SYN jnz .respond_seg_syn -.drop_no_socket: - - DEBUGF 1,"TCP_input: Drop (no socket)\n" - - call kernel_free - add esp, 4 - ret + jmp .drop_no_socket .respond_seg_ack: diff --git a/kernel/branches/net/network/tcp_subr.inc b/kernel/branches/net/network/tcp_subr.inc index 8710074a81..d8e7658010 100644 --- a/kernel/branches/net/network/tcp_subr.inc +++ b/kernel/branches/net/network/tcp_subr.inc @@ -82,7 +82,7 @@ macro TCP_rcvseqinit ptr { -macro TCP_init_socket socket { +macro TCP_init_socket socket { mov [socket + TCP_SOCKET.t_maxseg], TCP_mss_default mov [socket + TCP_SOCKET.t_flags], 0 ; we could also request scale and timestamp @@ -487,3 +487,13 @@ macro TCP_set_persist socket { ; tp->t_rxtshift++; } + +; eax = rtt +; ebx = socket ptr + +align 4 +TCP_xmit_timer: + +;TODO: update srtt and rttvar + +ret