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); u32 ccmps = dccp_determine_ccmps(dp); u32 cur_mps = ccmps ? min(pmtu, ccmps) : pmtu; /* 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)); /* * Leave enough headroom for common DCCP header options. * This only considers options which may appear on DCCP-Data packets, as * per table 3 in RFC 4340, 5.8. When running out of space for other * options (eg. Ack Vector which can take up to 255 bytes), it is better * to schedule a separate Ack. Thus we leave headroom for the following: * - 1 byte for Slow Receiver (11.6) * - 6 bytes for Timestamp (13.1) * - 10 bytes for Timestamp Echo (13.3) * - 8 bytes for NDP count (7.7, when activated) * - 6 bytes for Data Checksum (9.3) * - %DCCPAV_MIN_OPTLEN bytes for Ack Vector size (11.4, when enabled) */ cur_mps -= roundup(1 + 6 + 10 + dp->dccps_send_ndp_count * 8 + 6 + (dp->dccps_hc_rx_ackvec ? DCCPAV_MIN_OPTLEN : 0), 4); /* And store cached results */ icsk->icsk_pmtu_cookie = pmtu; dp->dccps_mss_cache = cur_mps; return cur_mps; }
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); u32 ccmps = dccp_determine_ccmps(dp); int cur_mps = ccmps ? min(pmtu, ccmps) : pmtu; /* 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, * TFRC will say it wants TIMESTAMPS, ELAPSED time, etc, for now lets * put a rough estimate for NDP + TIMESTAMP + TIMESTAMP_ECHO + ELAPSED * TIME + TFRC_OPT_LOSS_EVENT_RATE + TFRC_OPT_RECEIVE_RATE + padding to * make it a multiple of 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 = cur_mps; return cur_mps; }
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); u32 ccmps = dccp_determine_ccmps(dp); u32 cur_mps = ccmps ? min(pmtu, ccmps) : pmtu; cur_mps -= (icsk->icsk_af_ops->net_header_len + icsk->icsk_ext_hdr_len + sizeof(struct dccp_hdr) + sizeof(struct dccp_hdr_ext)); cur_mps -= roundup(1 + 6 + 10 + dp->dccps_send_ndp_count * 8 + 6 + (dp->dccps_hc_rx_ackvec ? DCCPAV_MIN_OPTLEN : 0), 4); icsk->icsk_pmtu_cookie = pmtu; dp->dccps_mss_cache = cur_mps; return cur_mps; }