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linux-brain/include/rxrpc/packet.h
David Howells 248f219cb8 rxrpc: Rewrite the data and ack handling code 
Rewrite the data and ack handling code such that:

 (1) Parsing of received ACK and ABORT packets and the distribution and the
     filing of DATA packets happens entirely within the data_ready context
     called from the UDP socket.  This allows us to process and discard ACK
     and ABORT packets much more quickly (they're no longer stashed on a
     queue for a background thread to process).

 (2) We avoid calling skb_clone(), pskb_pull() and pskb_trim().  We instead
     keep track of the offset and length of the content of each packet in
     the sk_buff metadata.  This means we don't do any allocation in the
     receive path.

 (3) Jumbo DATA packet parsing is now done in data_ready context.  Rather
     than cloning the packet once for each subpacket and pulling/trimming
     it, we file the packet multiple times with an annotation for each
     indicating which subpacket is there.  From that we can directly
     calculate the offset and length.

 (4) A call's receive queue can be accessed without taking locks (memory
     barriers do have to be used, though).

 (5) Incoming calls are set up from preallocated resources and immediately
     made live.  They can than have packets queued upon them and ACKs
     generated.  If insufficient resources exist, DATA packet #1 is given a
     BUSY reply and other DATA packets are discarded).

 (6) sk_buffs no longer take a ref on their parent call.

To make this work, the following changes are made:

 (1) Each call's receive buffer is now a circular buffer of sk_buff
     pointers (rxtx_buffer) rather than a number of sk_buff_heads spread
     between the call and the socket.  This permits each sk_buff to be in
     the buffer multiple times.  The receive buffer is reused for the
     transmit buffer.

 (2) A circular buffer of annotations (rxtx_annotations) is kept parallel
     to the data buffer.  Transmission phase annotations indicate whether a
     buffered packet has been ACK'd or not and whether it needs
     retransmission.

     Receive phase annotations indicate whether a slot holds a whole packet
     or a jumbo subpacket and, if the latter, which subpacket.  They also
     note whether the packet has been decrypted in place.

 (3) DATA packet window tracking is much simplified.  Each phase has just
     two numbers representing the window (rx_hard_ack/rx_top and
     tx_hard_ack/tx_top).

     The hard_ack number is the sequence number before base of the window,
     representing the last packet the other side says it has consumed.
     hard_ack starts from 0 and the first packet is sequence number 1.

     The top number is the sequence number of the highest-numbered packet
     residing in the buffer.  Packets between hard_ack+1 and top are
     soft-ACK'd to indicate they've been received, but not yet consumed.

     Four macros, before(), before_eq(), after() and after_eq() are added
     to compare sequence numbers within the window.  This allows for the
     top of the window to wrap when the hard-ack sequence number gets close
     to the limit.

     Two flags, RXRPC_CALL_RX_LAST and RXRPC_CALL_TX_LAST, are added also
     to indicate when rx_top and tx_top point at the packets with the
     LAST_PACKET bit set, indicating the end of the phase.

 (4) Calls are queued on the socket 'receive queue' rather than packets.
     This means that we don't need have to invent dummy packets to queue to
     indicate abnormal/terminal states and we don't have to keep metadata
     packets (such as ABORTs) around

 (5) The offset and length of a (sub)packet's content are now passed to
     the verify_packet security op.  This is currently expected to decrypt
     the packet in place and validate it.

     However, there's now nowhere to store the revised offset and length of
     the actual data within the decrypted blob (there may be a header and
     padding to skip) because an sk_buff may represent multiple packets, so
     a locate_data security op is added to retrieve these details from the
     sk_buff content when needed.

 (6) recvmsg() now has to handle jumbo subpackets, where each subpacket is
     individually secured and needs to be individually decrypted.  The code
     to do this is broken out into rxrpc_recvmsg_data() and shared with the
     kernel API.  It now iterates over the call's receive buffer rather
     than walking the socket receive queue.

Additional changes:

 (1) The timers are condensed to a single timer that is set for the soonest
     of three timeouts (delayed ACK generation, DATA retransmission and
     call lifespan).

 (2) Transmission of ACK and ABORT packets is effected immediately from
     process-context socket ops/kernel API calls that cause them instead of
     them being punted off to a background work item.  The data_ready
     handler still has to defer to the background, though.

 (3) A shutdown op is added to the AF_RXRPC socket so that the AFS
     filesystem can shut down the socket and flush its own work items
     before closing the socket to deal with any in-progress service calls.

Future additional changes that will need to be considered:

 (1) Make sure that a call doesn't hog the front of the queue by receiving
     data from the network as fast as userspace is consuming it to the
     exclusion of other calls.

 (2) Transmit delayed ACKs from within recvmsg() when we've consumed
     sufficiently more packets to avoid the background work item needing to
     run.

Signed-off-by: David Howells <dhowells@redhat.com>
2016-09-08 11:10:12 +01:00

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/* packet.h: Rx packet layout and definitions
*
* Copyright (C) 2002, 2007 Red Hat, Inc. All Rights Reserved.
* Written by David Howells (dhowells@redhat.com)
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version
* 2 of the License, or (at your option) any later version.
*/
#ifndef _LINUX_RXRPC_PACKET_H
#define _LINUX_RXRPC_PACKET_H
typedef u32 rxrpc_seq_t; /* Rx message sequence number */
typedef u32 rxrpc_serial_t; /* Rx message serial number */
typedef __be32 rxrpc_seq_net_t; /* on-the-wire Rx message sequence number */
typedef __be32 rxrpc_serial_net_t; /* on-the-wire Rx message serial number */
/*****************************************************************************/
/*
* on-the-wire Rx packet header
* - all multibyte fields should be in network byte order
*/
struct rxrpc_wire_header {
__be32 epoch; /* client boot timestamp */
#define RXRPC_RANDOM_EPOCH 0x80000000 /* Random if set, date-based if not */
__be32 cid; /* connection and channel ID */
#define RXRPC_MAXCALLS 4 /* max active calls per conn */
#define RXRPC_CHANNELMASK (RXRPC_MAXCALLS-1) /* mask for channel ID */
#define RXRPC_CIDMASK (~RXRPC_CHANNELMASK) /* mask for connection ID */
#define RXRPC_CIDSHIFT ilog2(RXRPC_MAXCALLS) /* shift for connection ID */
#define RXRPC_CID_INC (1 << RXRPC_CIDSHIFT) /* connection ID increment */
__be32 callNumber; /* call ID (0 for connection-level packets) */
__be32 seq; /* sequence number of pkt in call stream */
__be32 serial; /* serial number of pkt sent to network */
uint8_t type; /* packet type */
#define RXRPC_PACKET_TYPE_DATA 1 /* data */
#define RXRPC_PACKET_TYPE_ACK 2 /* ACK */
#define RXRPC_PACKET_TYPE_BUSY 3 /* call reject */
#define RXRPC_PACKET_TYPE_ABORT 4 /* call/connection abort */
#define RXRPC_PACKET_TYPE_ACKALL 5 /* ACK all outstanding packets on call */
#define RXRPC_PACKET_TYPE_CHALLENGE 6 /* connection security challenge (SRVR->CLNT) */
#define RXRPC_PACKET_TYPE_RESPONSE 7 /* connection secutity response (CLNT->SRVR) */
#define RXRPC_PACKET_TYPE_DEBUG 8 /* debug info request */
#define RXRPC_PACKET_TYPE_VERSION 13 /* version string request */
#define RXRPC_N_PACKET_TYPES 14 /* number of packet types (incl type 0) */
uint8_t flags; /* packet flags */
#define RXRPC_CLIENT_INITIATED 0x01 /* signifies a packet generated by a client */
#define RXRPC_REQUEST_ACK 0x02 /* request an unconditional ACK of this packet */
#define RXRPC_LAST_PACKET 0x04 /* the last packet from this side for this call */
#define RXRPC_MORE_PACKETS 0x08 /* more packets to come */
#define RXRPC_JUMBO_PACKET 0x20 /* [DATA] this is a jumbo packet */
#define RXRPC_SLOW_START_OK 0x20 /* [ACK] slow start supported */
uint8_t userStatus; /* app-layer defined status */
uint8_t securityIndex; /* security protocol ID */
union {
__be16 _rsvd; /* reserved */
__be16 cksum; /* kerberos security checksum */
};
__be16 serviceId; /* service ID */
} __packed;
#define RXRPC_SUPPORTED_PACKET_TYPES ( \
(1 << RXRPC_PACKET_TYPE_DATA) | \
(1 << RXRPC_PACKET_TYPE_ACK) | \
(1 << RXRPC_PACKET_TYPE_BUSY) | \
(1 << RXRPC_PACKET_TYPE_ABORT) | \
(1 << RXRPC_PACKET_TYPE_ACKALL) | \
(1 << RXRPC_PACKET_TYPE_CHALLENGE) | \
(1 << RXRPC_PACKET_TYPE_RESPONSE) | \
/*(1 << RXRPC_PACKET_TYPE_DEBUG) | */ \
(1 << RXRPC_PACKET_TYPE_VERSION))
/*****************************************************************************/
/*
* jumbo packet secondary header
* - can be mapped to read header by:
* - new_serial = serial + 1
* - new_seq = seq + 1
* - new_flags = j_flags
* - new__rsvd = j__rsvd
* - duplicating all other fields
*/
struct rxrpc_jumbo_header {
uint8_t flags; /* packet flags (as per rxrpc_header) */
uint8_t pad;
union {
__be16 _rsvd; /* reserved */
__be16 cksum; /* kerberos security checksum */
};
};
#define RXRPC_JUMBO_DATALEN 1412 /* non-terminal jumbo packet data length */
#define RXRPC_JUMBO_SUBPKTLEN (RXRPC_JUMBO_DATALEN + sizeof(struct rxrpc_jumbo_header))
/*****************************************************************************/
/*
* on-the-wire Rx ACK packet data payload
* - all multibyte fields should be in network byte order
*/
struct rxrpc_ackpacket {
__be16 bufferSpace; /* number of packet buffers available */
__be16 maxSkew; /* diff between serno being ACK'd and highest serial no
* received */
__be32 firstPacket; /* sequence no of first ACK'd packet in attached list */
__be32 previousPacket; /* sequence no of previous packet received */
__be32 serial; /* serial no of packet that prompted this ACK */
uint8_t reason; /* reason for ACK */
#define RXRPC_ACK_REQUESTED 1 /* ACK was requested on packet */
#define RXRPC_ACK_DUPLICATE 2 /* duplicate packet received */
#define RXRPC_ACK_OUT_OF_SEQUENCE 3 /* out of sequence packet received */
#define RXRPC_ACK_EXCEEDS_WINDOW 4 /* packet received beyond end of ACK window */
#define RXRPC_ACK_NOSPACE 5 /* packet discarded due to lack of buffer space */
#define RXRPC_ACK_PING 6 /* keep alive ACK */
#define RXRPC_ACK_PING_RESPONSE 7 /* response to RXRPC_ACK_PING */
#define RXRPC_ACK_DELAY 8 /* nothing happened since received packet */
#define RXRPC_ACK_IDLE 9 /* ACK due to fully received ACK window */
uint8_t nAcks; /* number of ACKs */
#define RXRPC_MAXACKS 255
uint8_t acks[0]; /* list of ACK/NAKs */
#define RXRPC_ACK_TYPE_NACK 0
#define RXRPC_ACK_TYPE_ACK 1
} __packed;
/* Some ACKs refer to specific packets and some are general and can be updated. */
#define RXRPC_ACK_UPDATEABLE ((1 << RXRPC_ACK_REQUESTED) | \
(1 << RXRPC_ACK_PING_RESPONSE) | \
(1 << RXRPC_ACK_DELAY) | \
(1 << RXRPC_ACK_IDLE))
/*
* ACK packets can have a further piece of information tagged on the end
*/
struct rxrpc_ackinfo {
__be32 rxMTU; /* maximum Rx MTU size (bytes) [AFS 3.3] */
__be32 maxMTU; /* maximum interface MTU size (bytes) [AFS 3.3] */
__be32 rwind; /* Rx window size (packets) [AFS 3.4] */
__be32 jumbo_max; /* max packets to stick into a jumbo packet [AFS 3.5] */
};
/*****************************************************************************/
/*
* Kerberos security type-2 challenge packet
*/
struct rxkad_challenge {
__be32 version; /* version of this challenge type */
__be32 nonce; /* encrypted random number */
__be32 min_level; /* minimum security level */
__be32 __padding; /* padding to 8-byte boundary */
} __packed;
/*****************************************************************************/
/*
* Kerberos security type-2 response packet
*/
struct rxkad_response {
__be32 version; /* version of this response type */
__be32 __pad;
/* encrypted bit of the response */
struct {
__be32 epoch; /* current epoch */
__be32 cid; /* parent connection ID */
__be32 checksum; /* checksum */
__be32 securityIndex; /* security type */
__be32 call_id[4]; /* encrypted call IDs */
__be32 inc_nonce; /* challenge nonce + 1 */
__be32 level; /* desired level */
} encrypted;
__be32 kvno; /* Kerberos key version number */
__be32 ticket_len; /* Kerberos ticket length */
} __packed;
/*****************************************************************************/
/*
* RxRPC-level abort codes
*/
#define RX_CALL_DEAD -1 /* call/conn has been inactive and is shut down */
#define RX_INVALID_OPERATION -2 /* invalid operation requested / attempted */
#define RX_CALL_TIMEOUT -3 /* call timeout exceeded */
#define RX_EOF -4 /* unexpected end of data on read op */
#define RX_PROTOCOL_ERROR -5 /* low-level protocol error */
#define RX_USER_ABORT -6 /* generic user abort */
#define RX_ADDRINUSE -7 /* UDP port in use */
#define RX_DEBUGI_BADTYPE -8 /* bad debugging packet type */
/*
* (un)marshalling abort codes (rxgen)
*/
#define RXGEN_CC_MARSHAL -450
#define RXGEN_CC_UNMARSHAL -451
#define RXGEN_SS_MARSHAL -452
#define RXGEN_SS_UNMARSHAL -453
#define RXGEN_DECODE -454
#define RXGEN_OPCODE -455
#define RXGEN_SS_XDRFREE -456
#define RXGEN_CC_XDRFREE -457
/*
* Rx kerberos security abort codes
* - unfortunately we have no generalised security abort codes to say things
* like "unsupported security", so we have to use these instead and hope the
* other side understands
*/
#define RXKADINCONSISTENCY 19270400 /* security module structure inconsistent */
#define RXKADPACKETSHORT 19270401 /* packet too short for security challenge */
#define RXKADLEVELFAIL 19270402 /* security level negotiation failed */
#define RXKADTICKETLEN 19270403 /* ticket length too short or too long */
#define RXKADOUTOFSEQUENCE 19270404 /* packet had bad sequence number */
#define RXKADNOAUTH 19270405 /* caller not authorised */
#define RXKADBADKEY 19270406 /* illegal key: bad parity or weak */
#define RXKADBADTICKET 19270407 /* security object was passed a bad ticket */
#define RXKADUNKNOWNKEY 19270408 /* ticket contained unknown key version number */
#define RXKADEXPIRED 19270409 /* authentication expired */
#define RXKADSEALEDINCON 19270410 /* sealed data inconsistent */
#define RXKADDATALEN 19270411 /* user data too long */
#define RXKADILLEGALLEVEL 19270412 /* caller not authorised to use encrypted conns */
#endif /* _LINUX_RXRPC_PACKET_H */
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