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-rw-r--r--net/dccp/ccid.h2
-rw-r--r--net/dccp/output.c30
2 files changed, 25 insertions, 7 deletions
diff --git a/net/dccp/ccid.h b/net/dccp/ccid.h
index e3cdd8afc80..fdeae7b5731 100644
--- a/net/dccp/ccid.h
+++ b/net/dccp/ccid.h
@@ -27,6 +27,7 @@ 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_owner: module which implements/owns this CCID
* @ccid_hc_{r,t}x_slab: memory pool for the receiver/sender half-connection
@@ -45,6 +46,7 @@ struct tcp_info;
*/
struct ccid_operations {
unsigned char ccid_id;
+ __u32 ccid_ccmps;
const char *ccid_name;
struct module *ccid_owner;
struct kmem_cache *ccid_hc_rx_slab,
diff --git a/net/dccp/output.c b/net/dccp/output.c
index 5589a5e581f..3b763db3d86 100644
--- a/net/dccp/output.c
+++ b/net/dccp/output.c
@@ -133,15 +133,31 @@ static int dccp_transmit_skb(struct sock *sk, struct sk_buff *skb)
return -ENOBUFS;
}
+/**
+ * dccp_determine_ccmps - Find out about CCID-specfic packet-size limits
+ * We only consider the HC-sender CCID for setting the CCMPS (RFC 4340, 14.),
+ * since the RX CCID is restricted to feedback packets (Acks), which are small
+ * in comparison with the data traffic. A value of 0 means "no current CCMPS".
+ */
+static u32 dccp_determine_ccmps(const struct dccp_sock *dp)
+{
+ const struct ccid *tx_ccid = dp->dccps_hc_tx_ccid;
+
+ if (tx_ccid == NULL || tx_ccid->ccid_ops == NULL)
+ return 0;
+ return tx_ccid->ccid_ops->ccid_ccmps;
+}
+
unsigned int dccp_sync_mss(struct sock *sk, u32 pmtu)
{
struct inet_connection_sock *icsk = inet_csk(sk);
struct dccp_sock *dp = dccp_sk(sk);
- int mss_now = (pmtu - icsk->icsk_af_ops->net_header_len -
- sizeof(struct dccp_hdr) - sizeof(struct dccp_hdr_ext));
+ u32 ccmps = dccp_determine_ccmps(dp);
+ int cur_mps = ccmps ? min(pmtu, ccmps) : pmtu;
- /* Now subtract optional transport overhead */
- mss_now -= icsk->icsk_ext_hdr_len;
+ /* Account for header lengths and IPv4/v6 option overhead */
+ cur_mps -= (icsk->icsk_af_ops->net_header_len + icsk->icsk_ext_hdr_len +
+ sizeof(struct dccp_hdr) + sizeof(struct dccp_hdr_ext));
/*
* FIXME: this should come from the CCID infrastructure, where, say,
@@ -151,13 +167,13 @@ unsigned int dccp_sync_mss(struct sock *sk, u32 pmtu)
* make it a multiple of 4
*/
- mss_now -= ((5 + 6 + 10 + 6 + 6 + 6 + 3) / 4) * 4;
+ cur_mps -= ((5 + 6 + 10 + 6 + 6 + 6 + 3) / 4) * 4;
/* And store cached results */
icsk->icsk_pmtu_cookie = pmtu;
- dp->dccps_mss_cache = mss_now;
+ dp->dccps_mss_cache = cur_mps;
- return mss_now;
+ return cur_mps;
}
EXPORT_SYMBOL_GPL(dccp_sync_mss);