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tcp: add const qualifiers where possible
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Adding const qualifiers to pointers can ease code review, and spot some
bugs. It might allow compiler to optimize code further.

For example, is it legal to temporary write a null cksum into tcphdr
in tcp_md5_hash_header() ? I am afraid a sniffer could catch the
temporary null value...

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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Eric Dumazet authored and David S. Miller committed Oct 21, 2011
1 parent f04565d commit cf533ea
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Showing 11 changed files with 160 additions and 152 deletions.
2 changes: 1 addition & 1 deletion include/net/secure_seq.h
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Original file line number Diff line number Diff line change
Expand Up @@ -10,7 +10,7 @@ extern u32 secure_ipv6_port_ephemeral(const __be32 *saddr, const __be32 *daddr,
__be16 dport);
extern __u32 secure_tcp_sequence_number(__be32 saddr, __be32 daddr,
__be16 sport, __be16 dport);
extern __u32 secure_tcpv6_sequence_number(__be32 *saddr, __be32 *daddr,
extern __u32 secure_tcpv6_sequence_number(const __be32 *saddr, const __be32 *daddr,
__be16 sport, __be16 dport);
extern u64 secure_dccp_sequence_number(__be32 saddr, __be32 daddr,
__be16 sport, __be16 dport);
Expand Down
43 changes: 23 additions & 20 deletions include/net/tcp.h
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Original file line number Diff line number Diff line change
Expand Up @@ -327,9 +327,9 @@ extern int tcp_sendpage(struct sock *sk, struct page *page, int offset,
size_t size, int flags);
extern int tcp_ioctl(struct sock *sk, int cmd, unsigned long arg);
extern int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb,
struct tcphdr *th, unsigned len);
const struct tcphdr *th, unsigned int len);
extern int tcp_rcv_established(struct sock *sk, struct sk_buff *skb,
struct tcphdr *th, unsigned len);
const struct tcphdr *th, unsigned int len);
extern void tcp_rcv_space_adjust(struct sock *sk);
extern void tcp_cleanup_rbuf(struct sock *sk, int copied);
extern int tcp_twsk_unique(struct sock *sk, struct sock *sktw, void *twp);
Expand Down Expand Up @@ -401,10 +401,10 @@ extern void tcp_set_keepalive(struct sock *sk, int val);
extern void tcp_syn_ack_timeout(struct sock *sk, struct request_sock *req);
extern int tcp_recvmsg(struct kiocb *iocb, struct sock *sk, struct msghdr *msg,
size_t len, int nonblock, int flags, int *addr_len);
extern void tcp_parse_options(struct sk_buff *skb,
struct tcp_options_received *opt_rx, u8 **hvpp,
extern void tcp_parse_options(const struct sk_buff *skb,
struct tcp_options_received *opt_rx, const u8 **hvpp,
int estab);
extern u8 *tcp_parse_md5sig_option(struct tcphdr *th);
extern const u8 *tcp_parse_md5sig_option(const struct tcphdr *th);

/*
* TCP v4 functions exported for the inet6 API
Expand Down Expand Up @@ -450,7 +450,7 @@ extern bool cookie_check_timestamp(struct tcp_options_received *opt, bool *);
/* From net/ipv6/syncookies.c */
extern struct sock *cookie_v6_check(struct sock *sk, struct sk_buff *skb);
#ifdef CONFIG_SYN_COOKIES
extern __u32 cookie_v6_init_sequence(struct sock *sk, struct sk_buff *skb,
extern __u32 cookie_v6_init_sequence(struct sock *sk, const struct sk_buff *skb,
__u16 *mss);
#else
static inline __u32 cookie_v6_init_sequence(struct sock *sk,
Expand Down Expand Up @@ -522,7 +522,7 @@ static inline int tcp_bound_to_half_wnd(struct tcp_sock *tp, int pktsize)
}

/* tcp.c */
extern void tcp_get_info(struct sock *, struct tcp_info *);
extern void tcp_get_info(const struct sock *, struct tcp_info *);

/* Read 'sendfile()'-style from a TCP socket */
typedef int (*sk_read_actor_t)(read_descriptor_t *, struct sk_buff *,
Expand All @@ -532,8 +532,8 @@ extern int tcp_read_sock(struct sock *sk, read_descriptor_t *desc,

extern void tcp_initialize_rcv_mss(struct sock *sk);

extern int tcp_mtu_to_mss(struct sock *sk, int pmtu);
extern int tcp_mss_to_mtu(struct sock *sk, int mss);
extern int tcp_mtu_to_mss(const struct sock *sk, int pmtu);
extern int tcp_mss_to_mtu(const struct sock *sk, int mss);
extern void tcp_mtup_init(struct sock *sk);
extern void tcp_valid_rtt_meas(struct sock *sk, u32 seq_rtt);

Expand Down Expand Up @@ -574,7 +574,7 @@ static inline void tcp_fast_path_check(struct sock *sk)
/* Compute the actual rto_min value */
static inline u32 tcp_rto_min(struct sock *sk)
{
struct dst_entry *dst = __sk_dst_get(sk);
const struct dst_entry *dst = __sk_dst_get(sk);
u32 rto_min = TCP_RTO_MIN;

if (dst && dst_metric_locked(dst, RTAX_RTO_MIN))
Expand Down Expand Up @@ -820,6 +820,7 @@ static inline bool tcp_in_initial_slowstart(const struct tcp_sock *tp)
static inline __u32 tcp_current_ssthresh(const struct sock *sk)
{
const struct tcp_sock *tp = tcp_sk(sk);

if ((1 << inet_csk(sk)->icsk_ca_state) & (TCPF_CA_CWR | TCPF_CA_Recovery))
return tp->snd_ssthresh;
else
Expand All @@ -832,7 +833,7 @@ static inline __u32 tcp_current_ssthresh(const struct sock *sk)
#define tcp_verify_left_out(tp) WARN_ON(tcp_left_out(tp) > tp->packets_out)

extern void tcp_enter_cwr(struct sock *sk, const int set_ssthresh);
extern __u32 tcp_init_cwnd(struct tcp_sock *tp, struct dst_entry *dst);
extern __u32 tcp_init_cwnd(const struct tcp_sock *tp, const struct dst_entry *dst);

/* Slow start with delack produces 3 packets of burst, so that
* it is safe "de facto". This will be the default - same as
Expand Down Expand Up @@ -861,7 +862,7 @@ static inline void tcp_minshall_update(struct tcp_sock *tp, unsigned int mss,

static inline void tcp_check_probe_timer(struct sock *sk)
{
struct tcp_sock *tp = tcp_sk(sk);
const struct tcp_sock *tp = tcp_sk(sk);
const struct inet_connection_sock *icsk = inet_csk(sk);

if (!tp->packets_out && !icsk->icsk_pending)
Expand Down Expand Up @@ -1209,10 +1210,10 @@ extern struct tcp_md5sig_pool *tcp_get_md5sig_pool(void);
extern void tcp_put_md5sig_pool(void);

extern int tcp_md5_hash_header(struct tcp_md5sig_pool *, struct tcphdr *);
extern int tcp_md5_hash_skb_data(struct tcp_md5sig_pool *, struct sk_buff *,
extern int tcp_md5_hash_skb_data(struct tcp_md5sig_pool *, const struct sk_buff *,
unsigned header_len);
extern int tcp_md5_hash_key(struct tcp_md5sig_pool *hp,
struct tcp_md5sig_key *key);
const struct tcp_md5sig_key *key);

/* write queue abstraction */
static inline void tcp_write_queue_purge(struct sock *sk)
Expand All @@ -1225,22 +1226,24 @@ static inline void tcp_write_queue_purge(struct sock *sk)
tcp_clear_all_retrans_hints(tcp_sk(sk));
}

static inline struct sk_buff *tcp_write_queue_head(struct sock *sk)
static inline struct sk_buff *tcp_write_queue_head(const struct sock *sk)
{
return skb_peek(&sk->sk_write_queue);
}

static inline struct sk_buff *tcp_write_queue_tail(struct sock *sk)
static inline struct sk_buff *tcp_write_queue_tail(const struct sock *sk)
{
return skb_peek_tail(&sk->sk_write_queue);
}

static inline struct sk_buff *tcp_write_queue_next(struct sock *sk, struct sk_buff *skb)
static inline struct sk_buff *tcp_write_queue_next(const struct sock *sk,
const struct sk_buff *skb)
{
return skb_queue_next(&sk->sk_write_queue, skb);
}

static inline struct sk_buff *tcp_write_queue_prev(struct sock *sk, struct sk_buff *skb)
static inline struct sk_buff *tcp_write_queue_prev(const struct sock *sk,
const struct sk_buff *skb)
{
return skb_queue_prev(&sk->sk_write_queue, skb);
}
Expand All @@ -1254,7 +1257,7 @@ static inline struct sk_buff *tcp_write_queue_prev(struct sock *sk, struct sk_bu
#define tcp_for_write_queue_from_safe(skb, tmp, sk) \
skb_queue_walk_from_safe(&(sk)->sk_write_queue, skb, tmp)

static inline struct sk_buff *tcp_send_head(struct sock *sk)
static inline struct sk_buff *tcp_send_head(const struct sock *sk)
{
return sk->sk_send_head;
}
Expand All @@ -1265,7 +1268,7 @@ static inline bool tcp_skb_is_last(const struct sock *sk,
return skb_queue_is_last(&sk->sk_write_queue, skb);
}

static inline void tcp_advance_send_head(struct sock *sk, struct sk_buff *skb)
static inline void tcp_advance_send_head(struct sock *sk, const struct sk_buff *skb)
{
if (tcp_skb_is_last(sk, skb))
sk->sk_send_head = NULL;
Expand Down
2 changes: 1 addition & 1 deletion net/core/secure_seq.c
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Original file line number Diff line number Diff line change
Expand Up @@ -35,7 +35,7 @@ static u32 seq_scale(u32 seq)
}

#if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE)
__u32 secure_tcpv6_sequence_number(__be32 *saddr, __be32 *daddr,
__u32 secure_tcpv6_sequence_number(const __be32 *saddr, const __be32 *daddr,
__be16 sport, __be16 dport)
{
u32 secret[MD5_MESSAGE_BYTES / 4];
Expand Down
2 changes: 1 addition & 1 deletion net/ipv4/syncookies.c
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Original file line number Diff line number Diff line change
Expand Up @@ -265,7 +265,7 @@ struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb,
struct ip_options *opt)
{
struct tcp_options_received tcp_opt;
u8 *hash_location;
const u8 *hash_location;
struct inet_request_sock *ireq;
struct tcp_request_sock *treq;
struct tcp_sock *tp = tcp_sk(sk);
Expand Down
18 changes: 9 additions & 9 deletions net/ipv4/tcp.c
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Original file line number Diff line number Diff line change
Expand Up @@ -374,7 +374,7 @@ unsigned int tcp_poll(struct file *file, struct socket *sock, poll_table *wait)
{
unsigned int mask;
struct sock *sk = sock->sk;
struct tcp_sock *tp = tcp_sk(sk);
const struct tcp_sock *tp = tcp_sk(sk);

sock_poll_wait(file, sk_sleep(sk), wait);
if (sk->sk_state == TCP_LISTEN)
Expand Down Expand Up @@ -528,7 +528,7 @@ static inline void tcp_mark_push(struct tcp_sock *tp, struct sk_buff *skb)
tp->pushed_seq = tp->write_seq;
}

static inline int forced_push(struct tcp_sock *tp)
static inline int forced_push(const struct tcp_sock *tp)
{
return after(tp->write_seq, tp->pushed_seq + (tp->max_window >> 1));
}
Expand Down Expand Up @@ -891,9 +891,9 @@ EXPORT_SYMBOL(tcp_sendpage);
#define TCP_PAGE(sk) (sk->sk_sndmsg_page)
#define TCP_OFF(sk) (sk->sk_sndmsg_off)

static inline int select_size(struct sock *sk, int sg)
static inline int select_size(const struct sock *sk, int sg)
{
struct tcp_sock *tp = tcp_sk(sk);
const struct tcp_sock *tp = tcp_sk(sk);
int tmp = tp->mss_cache;

if (sg) {
Expand Down Expand Up @@ -2408,7 +2408,7 @@ static int do_tcp_setsockopt(struct sock *sk, int level,
int tcp_setsockopt(struct sock *sk, int level, int optname, char __user *optval,
unsigned int optlen)
{
struct inet_connection_sock *icsk = inet_csk(sk);
const struct inet_connection_sock *icsk = inet_csk(sk);

if (level != SOL_TCP)
return icsk->icsk_af_ops->setsockopt(sk, level, optname,
Expand All @@ -2430,9 +2430,9 @@ EXPORT_SYMBOL(compat_tcp_setsockopt);
#endif

/* Return information about state of tcp endpoint in API format. */
void tcp_get_info(struct sock *sk, struct tcp_info *info)
void tcp_get_info(const struct sock *sk, struct tcp_info *info)
{
struct tcp_sock *tp = tcp_sk(sk);
const struct tcp_sock *tp = tcp_sk(sk);
const struct inet_connection_sock *icsk = inet_csk(sk);
u32 now = tcp_time_stamp;

Expand Down Expand Up @@ -3010,7 +3010,7 @@ int tcp_md5_hash_header(struct tcp_md5sig_pool *hp,
EXPORT_SYMBOL(tcp_md5_hash_header);

int tcp_md5_hash_skb_data(struct tcp_md5sig_pool *hp,
struct sk_buff *skb, unsigned header_len)
const struct sk_buff *skb, unsigned int header_len)
{
struct scatterlist sg;
const struct tcphdr *tp = tcp_hdr(skb);
Expand Down Expand Up @@ -3043,7 +3043,7 @@ int tcp_md5_hash_skb_data(struct tcp_md5sig_pool *hp,
}
EXPORT_SYMBOL(tcp_md5_hash_skb_data);

int tcp_md5_hash_key(struct tcp_md5sig_pool *hp, struct tcp_md5sig_key *key)
int tcp_md5_hash_key(struct tcp_md5sig_pool *hp, const struct tcp_md5sig_key *key)
{
struct scatterlist sg;

Expand Down
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