/* * net/dccp/output.c * * An implementation of the DCCP protocol * Arnaldo Carvalho de Melo <acme@conectiva.com.br> * * This program is free software; you can redistribute it and/or * modify it under the terms of the GNU General Public License * as published by the Free Software Foundation; either version * 2 of the License, or (at your option) any later version. */ #include <linux/dccp.h> #include <linux/kernel.h> #include <linux/skbuff.h> #include <linux/slab.h> #include <net/inet_sock.h> #include <net/sock.h> #include "ackvec.h" #include "ccid.h" #include "dccp.h" static inline void dccp_event_ack_sent(struct sock *sk) { inet_csk_clear_xmit_timer(sk, ICSK_TIME_DACK); } /* enqueue @skb on sk_send_head for retransmission, return clone to send now */ static struct sk_buff *dccp_skb_entail(struct sock *sk, struct sk_buff *skb) { skb_set_owner_w(skb, sk); WARN_ON(sk->sk_send_head); sk->sk_send_head = skb; return skb_clone(sk->sk_send_head, gfp_any()); } /* * All SKB's seen here are completely headerless. It is our * job to build the DCCP header, and pass the packet down to * IP so it can do the same plus pass the packet off to the * device. */ static int dccp_transmit_skb(struct sock *sk, struct sk_buff *skb) { if (likely(skb != NULL)) { struct inet_sock *inet = inet_sk(sk); const struct inet_connection_sock *icsk = inet_csk(sk); struct dccp_sock *dp = dccp_sk(sk); struct dccp_skb_cb *dcb = DCCP_SKB_CB(skb); struct dccp_hdr *dh; /* XXX For now we're using only 48 bits sequence numbers */ const u32 dccp_header_size = sizeof(*dh) + sizeof(struct dccp_hdr_ext) + dccp_packet_hdr_len(dcb->dccpd_type); int err, set_ack = 1; u64 ackno = dp->dccps_gsr; /* * Increment GSS here already in case the option code needs it. * Update GSS for real only if option processing below succeeds. */ dcb->dccpd_seq = ADD48(dp->dccps_gss, 1); switch (dcb->dccpd_type) { case DCCP_PKT_DATA: set_ack = 0; /* fall through */ case DCCP_PKT_DATAACK: case DCCP_PKT_RESET: break; case DCCP_PKT_REQUEST: set_ack = 0; /* Use ISS on the first (non-retransmitted) Request. */ if (icsk->icsk_retransmits == 0) dcb->dccpd_seq = dp->dccps_iss; /* fall through */ case DCCP_PKT_SYNC: case DCCP_PKT_SYNCACK: ackno = dcb->dccpd_ack_seq; /* fall through */ default: /* * Set owner/destructor: some skbs are allocated via * alloc_skb (e.g. when retransmission may happen). * Only Data, DataAck, and Reset packets should come * through here with skb->sk set. */ WARN_ON(skb->sk); skb_set_owner_w(skb, sk); break; } if (dccp_insert_options(sk, skb)) { kfree_skb(skb); return -EPROTO; } /* Build DCCP header and checksum it. */ dh = dccp_zeroed_hdr(skb, dccp_header_size); dh->dccph_type = dcb->dccpd_type; dh->dccph_sport = inet->inet_sport; dh->dccph_dport = inet->inet_dport; dh->dccph_doff = (dccp_header_size + dcb->dccpd_opt_len) / 4; dh->dccph_ccval = dcb->dccpd_ccval; dh->dccph_cscov = dp->dccps_pcslen; /* XXX For now we're using only 48 bits sequence numbers */ dh->dccph_x = 1; dccp_update_gss(sk, dcb->dccpd_seq); dccp_hdr_set_seq(dh, dp->dccps_gss); if (set_ack) dccp_hdr_set_ack(dccp_hdr_ack_bits(skb), ackno); switch (dcb->dccpd_type) { case DCCP_PKT_REQUEST: dccp_hdr_request(skb)->dccph_req_service = dp->dccps_service; /* * Limit Ack window to ISS <= P.ackno <= GSS, so that * only Responses to Requests we sent are considered. */ dp->dccps_awl = dp->dccps_iss; break; case DCCP_PKT_RESET: dccp_hdr_reset(skb)->dccph_reset_code = dcb->dccpd_reset_code; break; } icsk->icsk_af_ops->send_check(sk, skb); if (set_ack) dccp_event_ack_sent(sk); DCCP_INC_STATS(DCCP_MIB_OUTSEGS); err = icsk->icsk_af_ops->queue_xmit(sk, skb, &inet->cork.fl); return net_xmit_eval(err); } return -ENOBUFS; } /** * dccp_determine_ccmps - Find out about CCID-specific 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); 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; } EXPORT_SYMBOL_GPL(dccp_sync_mss); void dccp_write_space(struct sock *sk) { struct socket_wq *wq; rcu_read_lock(); wq = rcu_dereference(sk->sk_wq); if (skwq_has_sleeper(wq)) wake_up_interruptible(&wq->wait); /* Should agree with poll, otherwise some programs break */ if (sock_writeable(sk)) sk_wake_async(sk, SOCK_WAKE_SPACE, POLL_OUT); rcu_read_unlock(); } /** * dccp_wait_for_ccid - Await CCID send permission * @sk: socket to wait for * @delay: timeout in jiffies * * This is used by CCIDs which need to delay the send time in process context. */ static int dccp_wait_for_ccid(struct sock *sk, unsigned long delay) { DEFINE_WAIT(wait); long remaining; prepare_to_wait(sk_sleep(sk), &wait, TASK_INTERRUPTIBLE); sk->sk_write_pending++; release_sock(sk); remaining = schedule_timeout(delay); lock_sock(sk); sk->sk_write_pending--; finish_wait(sk_sleep(sk), &wait); if (signal_pending(current) || sk->sk_err) return -1; return remaining; } /** * dccp_xmit_packet - Send data packet under control of CCID * Transmits next-queued payload and informs CCID to account for the packet. */ static void dccp_xmit_packet(struct sock *sk) { int err, len; struct dccp_sock *dp = dccp_sk(sk); struct sk_buff *skb = dccp_qpolicy_pop(sk); if (unlikely(skb == NULL)) return; len = skb->len; if (sk->sk_state == DCCP_PARTOPEN) { const u32 cur_mps = dp->dccps_mss_cache - DCCP_FEATNEG_OVERHEAD; /* * See 8.1.5 - Handshake Completion. * * For robustness we resend Confirm options until the client has * entered OPEN. During the initial feature negotiation, the MPS * is smaller than usual, reduced by the Change/Confirm options. */ if (!list_empty(&dp->dccps_featneg) && len > cur_mps) { DCCP_WARN("Payload too large (%d) for featneg.\n", len); dccp_send_ack(sk); dccp_feat_list_purge(&dp->dccps_featneg); } inet_csk_schedule_ack(sk); inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK, inet_csk(sk)->icsk_rto, DCCP_RTO_MAX); DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_DATAACK; } else if (dccp_ack_pending(sk)) { DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_DATAACK; } else { DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_DATA; } err = dccp_transmit_skb(sk, skb); if (err) dccp_pr_debug("transmit_skb() returned err=%d\n", err); /* * Register this one as sent even if an error occurred. To the remote * end a local packet drop is indistinguishable from network loss, i.e. * any local drop will eventually be reported via receiver feedback. */ ccid_hc_tx_packet_sent(dp->dccps_hc_tx_ccid, sk, len); /* * If the CCID needs to transfer additional header options out-of-band * (e.g. Ack Vectors or feature-negotiation options), it activates this * flag to schedule a Sync. The Sync will automatically incorporate all * currently pending header options, thus clearing the backlog. */ if (dp->dccps_sync_scheduled) dccp_send_sync(sk, dp->dccps_gsr, DCCP_PKT_SYNC); } /** * dccp_flush_write_queue - Drain queue at end of connection * Since dccp_sendmsg queues packets without waiting for them to be sent, it may * happen that the TX queue is not empty at the end of a connection. We give the * HC-sender CCID a grace period of up to @time_budget jiffies. If this function * returns with a non-empty write queue, it will be purged later. */ void dccp_flush_write_queue(struct sock *sk, long *time_budget) { struct dccp_sock *dp = dccp_sk(sk); struct sk_buff *skb; long delay, rc; while (*time_budget > 0 && (skb = skb_peek(&sk->sk_write_queue))) { rc = ccid_hc_tx_send_packet(dp->dccps_hc_tx_ccid, sk, skb); switch (ccid_packet_dequeue_eval(rc)) { case CCID_PACKET_WILL_DEQUEUE_LATER: /* * If the CCID determines when to send, the next sending * time is unknown or the CCID may not even send again * (e.g. remote host crashes or lost Ack packets). */ DCCP_WARN("CCID did not manage to send all packets\n"); return; case CCID_PACKET_DELAY: delay = msecs_to_jiffies(rc); if (delay > *time_budget) return; rc = dccp_wait_for_ccid(sk, delay); if (rc < 0) return; *time_budget -= (delay - rc); /* check again if we can send now */ break; case CCID_PACKET_SEND_AT_ONCE: dccp_xmit_packet(sk); break; case CCID_PACKET_ERR: skb_dequeue(&sk->sk_write_queue); kfree_skb(skb); dccp_pr_debug("packet discarded due to err=%ld\n", rc); } } } void dccp_write_xmit(struct sock *sk) { struct dccp_sock *dp = dccp_sk(sk); struct sk_buff *skb; while ((skb = dccp_qpolicy_top(sk))) { int rc = ccid_hc_tx_send_packet(dp->dccps_hc_tx_ccid, sk, skb); switch (ccid_packet_dequeue_eval(rc)) { case CCID_PACKET_WILL_DEQUEUE_LATER: return; case CCID_PACKET_DELAY: sk_reset_timer(sk, &dp->dccps_xmit_timer, jiffies + msecs_to_jiffies(rc)); return; case CCID_PACKET_SEND_AT_ONCE: dccp_xmit_packet(sk); break; case CCID_PACKET_ERR: dccp_qpolicy_drop(sk, skb); dccp_pr_debug("packet discarded due to err=%d\n", rc); } } } /** * 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. */ /* 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(const struct sock *sk, struct dst_entry *dst, struct request_sock *req) { struct dccp_hdr *dh; struct dccp_request_sock *dreq; const u32 dccp_header_size = sizeof(struct dccp_hdr) + sizeof(struct dccp_hdr_ext) + sizeof(struct dccp_hdr_response); struct sk_buff *skb; /* sk is marked const to clearly express we dont hold socket lock. * sock_wmalloc() will atomically change sk->sk_wmem_alloc, * it is safe to promote sk to non const. */ skb = sock_wmalloc((struct sock *)sk, MAX_DCCP_HEADER, 1, GFP_ATOMIC); if (!skb) return NULL; skb_reserve(skb, MAX_DCCP_HEADER); skb_dst_set(skb, dst_clone(dst)); dreq = dccp_rsk(req); if (inet_rsk(req)->acked) /* increase GSS upon retransmission */ dccp_inc_seqno(&dreq->dreq_gss); DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_RESPONSE; DCCP_SKB_CB(skb)->dccpd_seq = dreq->dreq_gss; /* Resolve feature dependencies resulting from choice of CCID */ if (dccp_feat_server_ccid_dependencies(dreq)) goto response_failed; if (dccp_insert_options_rsk(dreq, skb)) goto response_failed; /* Build and checksum header */ dh = dccp_zeroed_hdr(skb, dccp_header_size); dh->dccph_sport = htons(inet_rsk(req)->ir_num); dh->dccph_dport = inet_rsk(req)->ir_rmt_port; dh->dccph_doff = (dccp_header_size + DCCP_SKB_CB(skb)->dccpd_opt_len) / 4; dh->dccph_type = DCCP_PKT_RESPONSE; dh->dccph_x = 1; dccp_hdr_set_seq(dh, dreq->dreq_gss); dccp_hdr_set_ack(dccp_hdr_ack_bits(skb), dreq->dreq_gsr); dccp_hdr_response(skb)->dccph_resp_service = dreq->dreq_service; dccp_csum_outgoing(skb); /* We use `acked' to remember that a Response was already sent. */ inet_rsk(req)->acked = 1; DCCP_INC_STATS(DCCP_MIB_OUTSEGS); return skb; response_failed: kfree_skb(skb); return NULL; } EXPORT_SYMBOL_GPL(dccp_make_response); /* answer offending packet in @rcv_skb with Reset from control socket @ctl */ struct sk_buff *dccp_ctl_make_reset(struct sock *sk, struct sk_buff *rcv_skb) { struct dccp_hdr *rxdh = dccp_hdr(rcv_skb), *dh; struct dccp_skb_cb *dcb = DCCP_SKB_CB(rcv_skb); const u32 dccp_hdr_reset_len = sizeof(struct dccp_hdr) + sizeof(struct dccp_hdr_ext) + sizeof(struct dccp_hdr_reset); struct dccp_hdr_reset *dhr; struct sk_buff *skb; skb = alloc_skb(sk->sk_prot->max_header, GFP_ATOMIC); if (skb == NULL) return NULL; skb_reserve(skb, sk->sk_prot->max_header); /* Swap the send and the receive. */ dh = dccp_zeroed_hdr(skb, dccp_hdr_reset_len); dh->dccph_type = DCCP_PKT_RESET; dh->dccph_sport = rxdh->dccph_dport; dh->dccph_dport = rxdh->dccph_sport; dh->dccph_doff = dccp_hdr_reset_len / 4; dh->dccph_x = 1; dhr = dccp_hdr_reset(skb); dhr->dccph_reset_code = dcb->dccpd_reset_code; switch (dcb->dccpd_reset_code) { case DCCP_RESET_CODE_PACKET_ERROR: dhr->dccph_reset_data[0] = rxdh->dccph_type; break; case DCCP_RESET_CODE_OPTION_ERROR: /* fall through */ case DCCP_RESET_CODE_MANDATORY_ERROR: memcpy(dhr->dccph_reset_data, dcb->dccpd_reset_data, 3); break; } /* * From RFC 4340, 8.3.1: * If P.ackno exists, set R.seqno := P.ackno + 1. * Else set R.seqno := 0. */ if (dcb->dccpd_ack_seq != DCCP_PKT_WITHOUT_ACK_SEQ) dccp_hdr_set_seq(dh, ADD48(dcb->dccpd_ack_seq, 1)); dccp_hdr_set_ack(dccp_hdr_ack_bits(skb), dcb->dccpd_seq); dccp_csum_outgoing(skb); return skb; } EXPORT_SYMBOL_GPL(dccp_ctl_make_reset); /* send Reset on established socket, to close or abort the connection */ int dccp_send_reset(struct sock *sk, enum dccp_reset_codes code) { struct sk_buff *skb; /* * FIXME: what if rebuild_header fails? * Should we be doing a rebuild_header here? */ int err = inet_csk(sk)->icsk_af_ops->rebuild_header(sk); if (err != 0) return err; skb = sock_wmalloc(sk, sk->sk_prot->max_header, 1, GFP_ATOMIC); if (skb == NULL) return -ENOBUFS; /* Reserve space for headers and prepare control bits. */ skb_reserve(skb, sk->sk_prot->max_header); DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_RESET; DCCP_SKB_CB(skb)->dccpd_reset_code = code; return dccp_transmit_skb(sk, skb); } /* * Do all connect socket setups that can be done AF independent. */ int dccp_connect(struct sock *sk) { struct sk_buff *skb; struct dccp_sock *dp = dccp_sk(sk); struct dst_entry *dst = __sk_dst_get(sk); struct inet_connection_sock *icsk = inet_csk(sk); sk->sk_err = 0; sock_reset_flag(sk, SOCK_DONE); dccp_sync_mss(sk, dst_mtu(dst)); /* do not connect if feature negotiation setup fails */ if (dccp_feat_finalise_settings(dccp_sk(sk))) return -EPROTO; /* Initialise GAR as per 8.5; AWL/AWH are set in dccp_transmit_skb() */ dp->dccps_gar = dp->dccps_iss; skb = alloc_skb(sk->sk_prot->max_header, sk->sk_allocation); if (unlikely(skb == NULL)) return -ENOBUFS; /* Reserve space for headers. */ skb_reserve(skb, sk->sk_prot->max_header); DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_REQUEST; dccp_transmit_skb(sk, dccp_skb_entail(sk, skb)); DCCP_INC_STATS(DCCP_MIB_ACTIVEOPENS); /* Timer for repeating the REQUEST until an answer. */ icsk->icsk_retransmits = 0; inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, icsk->icsk_rto, DCCP_RTO_MAX); return 0; } EXPORT_SYMBOL_GPL(dccp_connect); void dccp_send_ack(struct sock *sk) { /* If we have been reset, we may not send again. */ if (sk->sk_state != DCCP_CLOSED) { struct sk_buff *skb = alloc_skb(sk->sk_prot->max_header, GFP_ATOMIC); if (skb == NULL) { inet_csk_schedule_ack(sk); inet_csk(sk)->icsk_ack.ato = TCP_ATO_MIN; inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK, TCP_DELACK_MAX, DCCP_RTO_MAX); return; } /* Reserve space for headers */ skb_reserve(skb, sk->sk_prot->max_header); DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_ACK; dccp_transmit_skb(sk, skb); } } EXPORT_SYMBOL_GPL(dccp_send_ack); #if 0 /* FIXME: Is this still necessary (11.3) - currently nowhere used by DCCP. */ void dccp_send_delayed_ack(struct sock *sk) { struct inet_connection_sock *icsk = inet_csk(sk); /* * FIXME: tune this timer. elapsed time fixes the skew, so no problem * with using 2s, and active senders also piggyback the ACK into a * DATAACK packet, so this is really for quiescent senders. */ unsigned long timeout = jiffies + 2 * HZ; /* Use new timeout only if there wasn't a older one earlier. */ if (icsk->icsk_ack.pending & ICSK_ACK_TIMER) { /* If delack timer was blocked or is about to expire, * send ACK now. * * FIXME: check the "about to expire" part */ if (icsk->icsk_ack.blocked) { dccp_send_ack(sk); return; } if (!time_before(timeout, icsk->icsk_ack.timeout)) timeout = icsk->icsk_ack.timeout; } icsk->icsk_ack.pending |= ICSK_ACK_SCHED | ICSK_ACK_TIMER; icsk->icsk_ack.timeout = timeout; sk_reset_timer(sk, &icsk->icsk_delack_timer, timeout); } #endif void dccp_send_sync(struct sock *sk, const u64 ackno, const enum dccp_pkt_type pkt_type) { /* * We are not putting this on the write queue, so * dccp_transmit_skb() will set the ownership to this * sock. */ struct sk_buff *skb = alloc_skb(sk->sk_prot->max_header, GFP_ATOMIC); if (skb == NULL) { /* FIXME: how to make sure the sync is sent? */ DCCP_CRIT("could not send %s", dccp_packet_name(pkt_type)); return; } /* Reserve space for headers and prepare control bits. */ skb_reserve(skb, sk->sk_prot->max_header); DCCP_SKB_CB(skb)->dccpd_type = pkt_type; DCCP_SKB_CB(skb)->dccpd_ack_seq = ackno; /* * Clear the flag in case the Sync was scheduled for out-of-band data, * such as carrying a long Ack Vector. */ dccp_sk(sk)->dccps_sync_scheduled = 0; dccp_transmit_skb(sk, skb); } EXPORT_SYMBOL_GPL(dccp_send_sync); /* * Send a DCCP_PKT_CLOSE/CLOSEREQ. The caller locks the socket for us. This * cannot be allowed to fail queueing a DCCP_PKT_CLOSE/CLOSEREQ frame under * any circumstances. */ void dccp_send_close(struct sock *sk, const int active) { struct dccp_sock *dp = dccp_sk(sk); struct sk_buff *skb; const gfp_t prio = active ? GFP_KERNEL : GFP_ATOMIC; skb = alloc_skb(sk->sk_prot->max_header, prio); if (skb == NULL) return; /* Reserve space for headers and prepare control bits. */ skb_reserve(skb, sk->sk_prot->max_header); if (dp->dccps_role == DCCP_ROLE_SERVER && !dp->dccps_server_timewait) DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_CLOSEREQ; else DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_CLOSE; if (active) { skb = dccp_skb_entail(sk, skb); /* * Retransmission timer for active-close: RFC 4340, 8.3 requires * to retransmit the Close/CloseReq until the CLOSING/CLOSEREQ * state can be left. The initial timeout is 2 RTTs. * Since RTT measurement is done by the CCIDs, there is no easy * way to get an RTT sample. The fallback RTT from RFC 4340, 3.4 * is too low (200ms); we use a high value to avoid unnecessary * retransmissions when the link RTT is > 0.2 seconds. * FIXME: Let main module sample RTTs and use that instead. */ inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, DCCP_TIMEOUT_INIT, DCCP_RTO_MAX); } dccp_transmit_skb(sk, skb); }