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dccp: Allow to distinguish original and retransmitted packets

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This patch allows the sender to distinguish original and retransmitted packets,
which is in particular needed for the retransmission of DCCP-Requests:
 * the first Request uses ISS (generated in net/dccp/ip*.c), and sets GSS = ISS;
 * all retransmitted Requests use GSS' = GSS + 1, so that the n-th retransmitted
   Request has sequence number ISS + n (mod 48).

To add generic support, the patch reorganises existing code so that:
 * icsk_retransmits == 0     for the original packet and
 * icsk_retransmits = n > 0  for the n-th retransmitted packet
at the time dccp_transmit_skb() is called, via dccp_retransmit_skb().
 
Thanks to Wei Yongjun for pointing this problem out.

Further changes:
----------------
 * removed the `skb' argument from dccp_retransmit_skb(), since sk_send_head
   is used for all retransmissions (the exception is client-Acks in PARTOPEN
   state, but these do not use sk_send_head);
 * since sk_send_head always contains the original skb (via dccp_entail()),
   skb_cloned() never evaluated to true and thus pskb_copy() was never used.

Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
This commit is contained in:
Gerrit Renker 2008-07-26 11:59:09 +01:00
parent cdec7e50a4
commit 59435444a1
3 changed files with 21 additions and 21 deletions
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2
net/dccp/dccp.h
View file

@ -226,7 +226,7 @@ static inline void dccp_csum_outgoing(struct sk_buff *skb)
extern void dccp_v4_send_check(struct sock *sk, int len, struct sk_buff *skb);
extern int dccp_retransmit_skb(struct sock *sk, struct sk_buff *skb);
extern int dccp_retransmit_skb(struct sock *sk);
extern void dccp_send_ack(struct sock *sk);
extern void dccp_reqsk_send_ack(struct sk_buff *sk, struct request_sock *rsk);

20
net/dccp/output.c
View file

@ -284,14 +284,26 @@ void dccp_write_xmit(struct sock *sk, int block)
}
}
int dccp_retransmit_skb(struct sock *sk, struct sk_buff *skb)
/**
* dccp_retransmit_skb - Retransmit Request, Close, or CloseReq packets
* There are only four retransmittable packet types in DCCP:
* - Request in client-REQUEST state (sec. 8.1.1),
* - CloseReq in server-CLOSEREQ state (sec. 8.3),
* - Close in node-CLOSING state (sec. 8.3),
* - Acks in client-PARTOPEN state (sec. 8.1.5, handled by dccp_delack_timer()).
* This function expects sk->sk_send_head to contain the original skb.
*/
int dccp_retransmit_skb(struct sock *sk)
{
WARN_ON(sk->sk_send_head == NULL);
if (inet_csk(sk)->icsk_af_ops->rebuild_header(sk) != 0)
return -EHOSTUNREACH; /* Routing failure or similar. */
return dccp_transmit_skb(sk, (skb_cloned(skb) ?
pskb_copy(skb, GFP_ATOMIC):
skb_clone(skb, GFP_ATOMIC)));
/* this count is used to distinguish original and retransmitted skb */
inet_csk(sk)->icsk_retransmits++;
return dccp_transmit_skb(sk, skb_clone(sk->sk_send_head, GFP_ATOMIC));
}
struct sk_buff *dccp_make_response(struct sock *sk, struct dst_entry *dst,

20
net/dccp/timer.c
View file

@ -98,22 +98,12 @@ static void dccp_retransmit_timer(struct sock *sk)
goto backoff;
}
/*
* sk->sk_send_head has to have one skb with
* DCCP_SKB_CB(skb)->dccpd_type set to one of the retransmittable DCCP
* packet types. The only packets eligible for retransmission are:
* -- Requests in client-REQUEST state (sec. 8.1.1)
* -- Acks in client-PARTOPEN state (sec. 8.1.5)
* -- CloseReq in server-CLOSEREQ state (sec. 8.3)
* -- Close in node-CLOSING state (sec. 8.3) */
WARN_ON(sk->sk_send_head == NULL);
/*
* More than than 4MSL (8 minutes) has passed, a RESET(aborted) was
* sent, no need to retransmit, this sock is dead.
*/
if (dccp_write_timeout(sk))
goto out;
return;
/*
* We want to know the number of packets retransmitted, not the
@ -122,30 +112,28 @@ static void dccp_retransmit_timer(struct sock *sk)
if (icsk->icsk_retransmits == 0)
DCCP_INC_STATS_BH(DCCP_MIB_TIMEOUTS);
if (dccp_retransmit_skb(sk, sk->sk_send_head) < 0) {
if (dccp_retransmit_skb(sk) != 0) {
/*
* Retransmission failed because of local congestion,
* do not backoff.
*/
if (icsk->icsk_retransmits == 0)
if (--icsk->icsk_retransmits == 0)
icsk->icsk_retransmits = 1;
inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
min(icsk->icsk_rto,
TCP_RESOURCE_PROBE_INTERVAL),
DCCP_RTO_MAX);
goto out;
return;
}
backoff:
icsk->icsk_backoff++;
icsk->icsk_retransmits++;
icsk->icsk_rto = min(icsk->icsk_rto << 1, DCCP_RTO_MAX);
inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, icsk->icsk_rto,
DCCP_RTO_MAX);
if (icsk->icsk_retransmits > sysctl_dccp_retries1)
__sk_dst_reset(sk);
out:;
}
static void dccp_write_timer(unsigned long data)