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linux/net/dccp/ccid.h
Gustavo A. R. Silva 8402a31dd8 net: dccp: Replace zero-length array with flexible-array member 
The current codebase makes use of the zero-length array language
extension to the C90 standard, but the preferred mechanism to declare
variable-length types such as these ones is a flexible array member[1][2],
introduced in C99:

struct foo {
        int stuff;
        struct boo array[];
};

By making use of the mechanism above, we will get a compiler warning
in case the flexible array does not occur last in the structure, which
will help us prevent some kind of undefined behavior bugs from being
inadvertently introduced[3] to the codebase from now on.

Also, notice that, dynamic memory allocations won't be affected by
this change:

"Flexible array members have incomplete type, and so the sizeof operator
may not be applied. As a quirk of the original implementation of
zero-length arrays, sizeof evaluates to zero."[1]

This issue was found with the help of Coccinelle.

[1] https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html
[2] https://github.com/KSPP/linux/issues/21
[3] commit 7649773293 ("cxgb3/l2t: Fix undefined behaviour")

Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2020-02-28 12:08:37 -08:00

263 lines
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/* SPDX-License-Identifier: GPL-2.0-only */
#ifndef _CCID_H
#define _CCID_H
/*
* net/dccp/ccid.h
*
* An implementation of the DCCP protocol
* Arnaldo Carvalho de Melo <acme@conectiva.com.br>
*
* CCID infrastructure
*/
#include <net/sock.h>
#include <linux/compiler.h>
#include <linux/dccp.h>
#include <linux/list.h>
#include <linux/module.h>
/* maximum value for a CCID (RFC 4340, 19.5) */
#define CCID_MAX 255
#define CCID_SLAB_NAME_LENGTH 32
struct tcp_info;
/**
* struct ccid_operations - Interface to Congestion-Control Infrastructure
*
* @ccid_id: numerical CCID ID (up to %CCID_MAX, cf. table 5 in RFC 4340, 10.)
* @ccid_ccmps: the CCMPS including network/transport headers (0 when disabled)
* @ccid_name: alphabetical identifier string for @ccid_id
* @ccid_hc_{r,t}x_slab: memory pool for the receiver/sender half-connection
* @ccid_hc_{r,t}x_obj_size: size of the receiver/sender half-connection socket
*
* @ccid_hc_{r,t}x_init: CCID-specific initialisation routine (before startup)
* @ccid_hc_{r,t}x_exit: CCID-specific cleanup routine (before destruction)
* @ccid_hc_rx_packet_recv: implements the HC-receiver side
* @ccid_hc_{r,t}x_parse_options: parsing routine for CCID/HC-specific options
* @ccid_hc_{r,t}x_insert_options: insert routine for CCID/HC-specific options
* @ccid_hc_tx_packet_recv: implements feedback processing for the HC-sender
* @ccid_hc_tx_send_packet: implements the sending part of the HC-sender
* @ccid_hc_tx_packet_sent: does accounting for packets in flight by HC-sender
* @ccid_hc_{r,t}x_get_info: INET_DIAG information for HC-receiver/sender
* @ccid_hc_{r,t}x_getsockopt: socket options specific to HC-receiver/sender
*/
struct ccid_operations {
unsigned char ccid_id;
__u32 ccid_ccmps;
const char *ccid_name;
struct kmem_cache *ccid_hc_rx_slab,
*ccid_hc_tx_slab;
char ccid_hc_rx_slab_name[CCID_SLAB_NAME_LENGTH];
char ccid_hc_tx_slab_name[CCID_SLAB_NAME_LENGTH];
__u32 ccid_hc_rx_obj_size,
ccid_hc_tx_obj_size;
/* Interface Routines */
int (*ccid_hc_rx_init)(struct ccid *ccid, struct sock *sk);
int (*ccid_hc_tx_init)(struct ccid *ccid, struct sock *sk);
void (*ccid_hc_rx_exit)(struct sock *sk);
void (*ccid_hc_tx_exit)(struct sock *sk);
void (*ccid_hc_rx_packet_recv)(struct sock *sk,
struct sk_buff *skb);
int (*ccid_hc_rx_parse_options)(struct sock *sk, u8 pkt,
u8 opt, u8 *val, u8 len);
int (*ccid_hc_rx_insert_options)(struct sock *sk,
struct sk_buff *skb);
void (*ccid_hc_tx_packet_recv)(struct sock *sk,
struct sk_buff *skb);
int (*ccid_hc_tx_parse_options)(struct sock *sk, u8 pkt,
u8 opt, u8 *val, u8 len);
int (*ccid_hc_tx_send_packet)(struct sock *sk,
struct sk_buff *skb);
void (*ccid_hc_tx_packet_sent)(struct sock *sk,
unsigned int len);
void (*ccid_hc_rx_get_info)(struct sock *sk,
struct tcp_info *info);
void (*ccid_hc_tx_get_info)(struct sock *sk,
struct tcp_info *info);
int (*ccid_hc_rx_getsockopt)(struct sock *sk,
const int optname, int len,
u32 __user *optval,
int __user *optlen);
int (*ccid_hc_tx_getsockopt)(struct sock *sk,
const int optname, int len,
u32 __user *optval,
int __user *optlen);
};
extern struct ccid_operations ccid2_ops;
#ifdef CONFIG_IP_DCCP_CCID3
extern struct ccid_operations ccid3_ops;
#endif
int ccid_initialize_builtins(void);
void ccid_cleanup_builtins(void);
struct ccid {
struct ccid_operations *ccid_ops;
char ccid_priv[];
};
static inline void *ccid_priv(const struct ccid *ccid)
{
return (void *)ccid->ccid_priv;
}
bool ccid_support_check(u8 const *ccid_array, u8 array_len);
int ccid_get_builtin_ccids(u8 **ccid_array, u8 *array_len);
int ccid_getsockopt_builtin_ccids(struct sock *sk, int len,
char __user *, int __user *);
struct ccid *ccid_new(const u8 id, struct sock *sk, bool rx);
static inline int ccid_get_current_rx_ccid(struct dccp_sock *dp)
{
struct ccid *ccid = dp->dccps_hc_rx_ccid;
if (ccid == NULL || ccid->ccid_ops == NULL)
return -1;
return ccid->ccid_ops->ccid_id;
}
static inline int ccid_get_current_tx_ccid(struct dccp_sock *dp)
{
struct ccid *ccid = dp->dccps_hc_tx_ccid;
if (ccid == NULL || ccid->ccid_ops == NULL)
return -1;
return ccid->ccid_ops->ccid_id;
}
void ccid_hc_rx_delete(struct ccid *ccid, struct sock *sk);
void ccid_hc_tx_delete(struct ccid *ccid, struct sock *sk);
/*
* Congestion control of queued data packets via CCID decision.
*
* The TX CCID performs its congestion-control by indicating whether and when a
* queued packet may be sent, using the return code of ccid_hc_tx_send_packet().
* The following modes are supported via the symbolic constants below:
* - timer-based pacing (CCID returns a delay value in milliseconds);
* - autonomous dequeueing (CCID internally schedules dccps_xmitlet).
*/
enum ccid_dequeueing_decision {
CCID_PACKET_SEND_AT_ONCE = 0x00000, /* "green light": no delay */
CCID_PACKET_DELAY_MAX = 0x0FFFF, /* maximum delay in msecs */
CCID_PACKET_DELAY = 0x10000, /* CCID msec-delay mode */
CCID_PACKET_WILL_DEQUEUE_LATER = 0x20000, /* CCID autonomous mode */
CCID_PACKET_ERR = 0xF0000, /* error condition */
};
static inline int ccid_packet_dequeue_eval(const int return_code)
{
if (return_code < 0)
return CCID_PACKET_ERR;
if (return_code == 0)
return CCID_PACKET_SEND_AT_ONCE;
if (return_code <= CCID_PACKET_DELAY_MAX)
return CCID_PACKET_DELAY;
return return_code;
}
static inline int ccid_hc_tx_send_packet(struct ccid *ccid, struct sock *sk,
struct sk_buff *skb)
{
if (ccid->ccid_ops->ccid_hc_tx_send_packet != NULL)
return ccid->ccid_ops->ccid_hc_tx_send_packet(sk, skb);
return CCID_PACKET_SEND_AT_ONCE;
}
static inline void ccid_hc_tx_packet_sent(struct ccid *ccid, struct sock *sk,
unsigned int len)
{
if (ccid->ccid_ops->ccid_hc_tx_packet_sent != NULL)
ccid->ccid_ops->ccid_hc_tx_packet_sent(sk, len);
}
static inline void ccid_hc_rx_packet_recv(struct ccid *ccid, struct sock *sk,
struct sk_buff *skb)
{
if (ccid->ccid_ops->ccid_hc_rx_packet_recv != NULL)
ccid->ccid_ops->ccid_hc_rx_packet_recv(sk, skb);
}
static inline void ccid_hc_tx_packet_recv(struct ccid *ccid, struct sock *sk,
struct sk_buff *skb)
{
if (ccid->ccid_ops->ccid_hc_tx_packet_recv != NULL)
ccid->ccid_ops->ccid_hc_tx_packet_recv(sk, skb);
}
/**
* ccid_hc_tx_parse_options - Parse CCID-specific options sent by the receiver
* @pkt: type of packet that @opt appears on (RFC 4340, 5.1)
* @opt: the CCID-specific option type (RFC 4340, 5.8 and 10.3)
* @val: value of @opt
* @len: length of @val in bytes
*/
static inline int ccid_hc_tx_parse_options(struct ccid *ccid, struct sock *sk,
u8 pkt, u8 opt, u8 *val, u8 len)
{
if (!ccid || !ccid->ccid_ops->ccid_hc_tx_parse_options)
return 0;
return ccid->ccid_ops->ccid_hc_tx_parse_options(sk, pkt, opt, val, len);
}
/**
* ccid_hc_rx_parse_options - Parse CCID-specific options sent by the sender
* Arguments are analogous to ccid_hc_tx_parse_options()
*/
static inline int ccid_hc_rx_parse_options(struct ccid *ccid, struct sock *sk,
u8 pkt, u8 opt, u8 *val, u8 len)
{
if (!ccid || !ccid->ccid_ops->ccid_hc_rx_parse_options)
return 0;
return ccid->ccid_ops->ccid_hc_rx_parse_options(sk, pkt, opt, val, len);
}
static inline int ccid_hc_rx_insert_options(struct ccid *ccid, struct sock *sk,
struct sk_buff *skb)
{
if (ccid->ccid_ops->ccid_hc_rx_insert_options != NULL)
return ccid->ccid_ops->ccid_hc_rx_insert_options(sk, skb);
return 0;
}
static inline void ccid_hc_rx_get_info(struct ccid *ccid, struct sock *sk,
struct tcp_info *info)
{
if (ccid->ccid_ops->ccid_hc_rx_get_info != NULL)
ccid->ccid_ops->ccid_hc_rx_get_info(sk, info);
}
static inline void ccid_hc_tx_get_info(struct ccid *ccid, struct sock *sk,
struct tcp_info *info)
{
if (ccid->ccid_ops->ccid_hc_tx_get_info != NULL)
ccid->ccid_ops->ccid_hc_tx_get_info(sk, info);
}
static inline int ccid_hc_rx_getsockopt(struct ccid *ccid, struct sock *sk,
const int optname, int len,
u32 __user *optval, int __user *optlen)
{
int rc = -ENOPROTOOPT;
if (ccid != NULL && ccid->ccid_ops->ccid_hc_rx_getsockopt != NULL)
rc = ccid->ccid_ops->ccid_hc_rx_getsockopt(sk, optname, len,
optval, optlen);
return rc;
}
static inline int ccid_hc_tx_getsockopt(struct ccid *ccid, struct sock *sk,
const int optname, int len,
u32 __user *optval, int __user *optlen)
{
int rc = -ENOPROTOOPT;
if (ccid != NULL && ccid->ccid_ops->ccid_hc_tx_getsockopt != NULL)
rc = ccid->ccid_ops->ccid_hc_tx_getsockopt(sk, optname, len,
optval, optlen);
return rc;
}
#endif /* _CCID_H */
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