dccp ccid-2: Separate option parsing from CCID processing

This patch replaces an almost identical replication of code: large parts
of dccp_parse_options() re-appeared as ccid2_ackvector() in ccid2.c.

Apart from the duplication, this caused two more problems:
 1. CCIDs should not need to be concerned with parsing header options;
 2. one can not assume that Ack Vectors appear as a contiguous area within an
    skb, it is legal to insert other options and/or padding in between. The
    current code would throw an error and stop reading in such a case.

Since Ack Vectors provide CCID-specific information, they are now processed
by the CCID directly, separating this functionality from the main DCCP code.

Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>

5 files changed, 100 insertions, 100 deletions

diff --git a/net/dccp/ackvec.c b/net/dccp/ackvec.c
index 66b8a51300c0..41819848bdda 100644
--- a/net/dccp/ackvec.c
+++ b/net/dccp/ackvec.c
@@ -343,6 +343,34 @@ free_records:
         }
 }
 
+/*
+ *      Routines to keep track of Ack Vectors received in an skb
+ */
+int dccp_ackvec_parsed_add(struct list_head *head, u8 *vec, u8 len, u8 nonce)
+{
+        struct dccp_ackvec_parsed *new = kmalloc(sizeof(*new), GFP_ATOMIC);
+
+        if (new == NULL)
+                return -ENOBUFS;
+        new->vec   = vec;
+        new->len   = len;
+        new->nonce = nonce;
+
+        list_add_tail(&new->node, head);
+        return 0;
+}
+EXPORT_SYMBOL_GPL(dccp_ackvec_parsed_add);
+
+void dccp_ackvec_parsed_cleanup(struct list_head *parsed_chunks)
+{
+        struct dccp_ackvec_parsed *cur, *next;
+
+        list_for_each_entry_safe(cur, next, parsed_chunks, node)
+                kfree(cur);
+        INIT_LIST_HEAD(parsed_chunks);
+}
+EXPORT_SYMBOL_GPL(dccp_ackvec_parsed_cleanup);
+
 int __init dccp_ackvec_init(void)
 {
         dccp_ackvec_slab = kmem_cache_create("dccp_ackvec",
diff --git a/net/dccp/ackvec.h b/net/dccp/ackvec.h
index e19b8d5ee05f..e2ab0627a5ff 100644
--- a/net/dccp/ackvec.h
+++ b/net/dccp/ackvec.h
@@ -114,4 +114,23 @@ static inline bool dccp_ackvec_is_empty(const struct dccp_ackvec *av)
 {
         return av->av_overflow == 0 && av->av_buf_head == av->av_buf_tail;
 }
+
+/**
+ * struct dccp_ackvec_parsed  -  Record offsets of Ack Vectors in skb
+ * @vec:        start of vector (offset into skb)
+ * @len:        length of @vec
+ * @nonce:      whether @vec had an ECN nonce of 0 or 1
+ * @node:       FIFO - arranged in descending order of ack_ackno
+ * This structure is used by CCIDs to access Ack Vectors in a received skb.
+ */
+struct dccp_ackvec_parsed {
+        u8               *vec,
+                         len,
+                         nonce:1;
+        struct list_head node;
+};
+
+extern int dccp_ackvec_parsed_add(struct list_head *head,
+                                  u8 *vec, u8 len, u8 nonce);
+extern void dccp_ackvec_parsed_cleanup(struct list_head *parsed_chunks);
 #endif /* _ACKVEC_H */
diff --git a/net/dccp/ccids/ccid2.c b/net/dccp/ccids/ccid2.c
index cb1b4a0d1877..e96d5e810039 100644
--- a/net/dccp/ccids/ccid2.c
+++ b/net/dccp/ccids/ccid2.c
@@ -246,68 +246,6 @@ static void ccid2_hc_tx_packet_sent(struct sock *sk, unsigned int len)
 #endif
 }
 
-/* XXX Lame code duplication!
- * returns -1 if none was found.
- * else returns the next offset to use in the function call.
- */
-static int ccid2_ackvector(struct sock *sk, struct sk_buff *skb, int offset,
-                           unsigned char **vec, unsigned char *veclen)
-{
-        const struct dccp_hdr *dh = dccp_hdr(skb);
-        unsigned char *options = (unsigned char *)dh + dccp_hdr_len(skb);
-        unsigned char *opt_ptr;
-        const unsigned char *opt_end = (unsigned char *)dh +
-                                        (dh->dccph_doff * 4);
-        unsigned char opt, len;
-        unsigned char *value;
-
-        BUG_ON(offset < 0);
-        options += offset;
-        opt_ptr = options;
-        if (opt_ptr >= opt_end)
-                return -1;
-
-        while (opt_ptr != opt_end) {
-                opt   = *opt_ptr++;
-                len   = 0;
-                value = NULL;
-
-                /* Check if this isn't a single byte option */
-                if (opt > DCCPO_MAX_RESERVED) {
-                        if (opt_ptr == opt_end)
-                                goto out_invalid_option;
-
-                        len = *opt_ptr++;
-                        if (len < 3)
-                                goto out_invalid_option;
-                        /*
-                         * Remove the type and len fields, leaving
-                         * just the value size
-                         */
-                        len     -= 2;
-                        value   = opt_ptr;
-                        opt_ptr += len;
-
-                        if (opt_ptr > opt_end)
-                                goto out_invalid_option;
-                }
-
-                switch (opt) {
-                case DCCPO_ACK_VECTOR_0:
-                case DCCPO_ACK_VECTOR_1:
-                        *vec    = value;
-                        *veclen = len;
-                        return offset + (opt_ptr - options);
-                }
-        }
-
-        return -1;
-
-out_invalid_option:
-        DCCP_BUG("Invalid option - this should not happen (previous parsing)!");
-        return -1;
-}
-
 /**
  * ccid2_rtt_estimator - Sample RTT and compute RTO using RFC2988 algorithm
  * This code is almost identical with TCP's tcp_rtt_estimator(), since
@@ -432,16 +370,28 @@ static void ccid2_congestion_event(struct sock *sk, struct ccid2_seq *seqp)
                 ccid2_change_l_ack_ratio(sk, hc->tx_cwnd);
 }
 
+static int ccid2_hc_tx_parse_options(struct sock *sk, u8 packet_type,
+                                     u8 option, u8 *optval, u8 optlen)
+{
+        struct ccid2_hc_tx_sock *hc = ccid2_hc_tx_sk(sk);
+
+        switch (option) {
+        case DCCPO_ACK_VECTOR_0:
+        case DCCPO_ACK_VECTOR_1:
+                return dccp_ackvec_parsed_add(&hc->tx_av_chunks, optval, optlen,
+                                              option - DCCPO_ACK_VECTOR_0);
+        }
+        return 0;
+}
+
 static void ccid2_hc_tx_packet_recv(struct sock *sk, struct sk_buff *skb)
 {
         struct dccp_sock *dp = dccp_sk(sk);
         struct ccid2_hc_tx_sock *hc = ccid2_hc_tx_sk(sk);
         const bool sender_was_blocked = ccid2_cwnd_network_limited(hc);
+        struct dccp_ackvec_parsed *avp;
         u64 ackno, seqno;
         struct ccid2_seq *seqp;
-        unsigned char *vector;
-        unsigned char veclen;
-        int offset = 0;
         int done = 0;
         unsigned int maxincr = 0;
 
@@ -475,17 +425,12 @@ static void ccid2_hc_tx_packet_recv(struct sock *sk, struct sk_buff *skb)
         }
 
         /* check forward path congestion */
-        /* still didn't send out new data packets */
-        if (hc->tx_seqh == hc->tx_seqt)
+        if (dccp_packet_without_ack(skb))
                 return;
 
-        switch (DCCP_SKB_CB(skb)->dccpd_type) {
-        case DCCP_PKT_ACK:
-        case DCCP_PKT_DATAACK:
-                break;
-        default:
-                return;
-        }
+        /* still didn't send out new data packets */
+        if (hc->tx_seqh == hc->tx_seqt)
+                goto done;
 
         ackno = DCCP_SKB_CB(skb)->dccpd_ack_seq;
         if (after48(ackno, hc->tx_high_ack))
@@ -509,15 +454,16 @@ static void ccid2_hc_tx_packet_recv(struct sock *sk, struct sk_buff *skb)
                 maxincr = DIV_ROUND_UP(dp->dccps_l_ack_ratio, 2);
 
         /* go through all ack vectors */
-        while ((offset = ccid2_ackvector(sk, skb, offset,
-                                         &vector, &veclen)) != -1) {
+        list_for_each_entry(avp, &hc->tx_av_chunks, node) {
                 /* go through this ack vector */
-                while (veclen--) {
-                        u64 ackno_end_rl = SUB48(ackno, dccp_ackvec_runlen(vector));
+                for (; avp->len--; avp->vec++) {
+                        u64 ackno_end_rl = SUB48(ackno,
+                                                 dccp_ackvec_runlen(avp->vec));
 
-                        ccid2_pr_debug("ackvec start:%llu end:%llu\n",
+                        ccid2_pr_debug("ackvec %llu |%u,%u|\n",
                                        (unsigned long long)ackno,
-                                       (unsigned long long)ackno_end_rl);
+                                       dccp_ackvec_state(avp->vec) >> 6,
+                                       dccp_ackvec_runlen(avp->vec));
                         /* if the seqno we are analyzing is larger than the
                          * current ackno, then move towards the tail of our
                          * seqnos.
@@ -536,7 +482,7 @@ static void ccid2_hc_tx_packet_recv(struct sock *sk, struct sk_buff *skb)
                          * run length
                          */
                         while (between48(seqp->ccid2s_seq,ackno_end_rl,ackno)) {
-                                const u8 state = dccp_ackvec_state(vector);
+                                const u8 state = dccp_ackvec_state(avp->vec);
 
                                 /* new packet received or marked */
                                 if (state != DCCPAV_NOT_RECEIVED &&
@@ -563,7 +509,6 @@ static void ccid2_hc_tx_packet_recv(struct sock *sk, struct sk_buff *skb)
                                 break;
 
                         ackno = SUB48(ackno_end_rl, 1);
-                        vector++;
                 }
                 if (done)
                         break;
@@ -631,10 +576,11 @@ static void ccid2_hc_tx_packet_recv(struct sock *sk, struct sk_buff *skb)
                 sk_stop_timer(sk, &hc->tx_rtotimer);
         else
                 sk_reset_timer(sk, &hc->tx_rtotimer, jiffies + hc->tx_rto);
-
+done:
         /* check if incoming Acks allow pending packets to be sent */
         if (sender_was_blocked && !ccid2_cwnd_network_limited(hc))
                 tasklet_schedule(&dccp_sk(sk)->dccps_xmitlet);
+        dccp_ackvec_parsed_cleanup(&hc->tx_av_chunks);
 }
 
 static int ccid2_hc_tx_init(struct ccid *ccid, struct sock *sk)
@@ -663,6 +609,7 @@ static int ccid2_hc_tx_init(struct ccid *ccid, struct sock *sk)
         hc->tx_last_cong = ccid2_time_stamp;
         setup_timer(&hc->tx_rtotimer, ccid2_hc_tx_rto_expire,
                         (unsigned long)sk);
+        INIT_LIST_HEAD(&hc->tx_av_chunks);
         return 0;
 }
 
@@ -696,16 +643,17 @@ static void ccid2_hc_rx_packet_recv(struct sock *sk, struct sk_buff *skb)
 }
 
 struct ccid_operations ccid2_ops = {
-        .ccid_id                = DCCPC_CCID2,
-        .ccid_name              = "TCP-like",
-        .ccid_hc_tx_obj_size    = sizeof(struct ccid2_hc_tx_sock),
-        .ccid_hc_tx_init        = ccid2_hc_tx_init,
-        .ccid_hc_tx_exit        = ccid2_hc_tx_exit,
-        .ccid_hc_tx_send_packet = ccid2_hc_tx_send_packet,
-        .ccid_hc_tx_packet_sent = ccid2_hc_tx_packet_sent,
-        .ccid_hc_tx_packet_recv = ccid2_hc_tx_packet_recv,
-        .ccid_hc_rx_obj_size    = sizeof(struct ccid2_hc_rx_sock),
-        .ccid_hc_rx_packet_recv = ccid2_hc_rx_packet_recv,
+        .ccid_id                  = DCCPC_CCID2,
+        .ccid_name                = "TCP-like",
+        .ccid_hc_tx_obj_size      = sizeof(struct ccid2_hc_tx_sock),
+        .ccid_hc_tx_init          = ccid2_hc_tx_init,
+        .ccid_hc_tx_exit          = ccid2_hc_tx_exit,
+        .ccid_hc_tx_send_packet   = ccid2_hc_tx_send_packet,
+        .ccid_hc_tx_packet_sent   = ccid2_hc_tx_packet_sent,
+        .ccid_hc_tx_parse_options = ccid2_hc_tx_parse_options,
+        .ccid_hc_tx_packet_recv   = ccid2_hc_tx_packet_recv,
+        .ccid_hc_rx_obj_size      = sizeof(struct ccid2_hc_rx_sock),
+        .ccid_hc_rx_packet_recv   = ccid2_hc_rx_packet_recv,
 };
 
 #ifdef CONFIG_IP_DCCP_CCID2_DEBUG
diff --git a/net/dccp/ccids/ccid2.h b/net/dccp/ccids/ccid2.h
index 25cb6b216eda..e9985dafc2c7 100644
--- a/net/dccp/ccids/ccid2.h
+++ b/net/dccp/ccids/ccid2.h
@@ -55,6 +55,7 @@ struct ccid2_seq {
  * @tx_rtt_seq:              to decay RTTVAR at most once per flight
  * @tx_rpseq:                last consecutive seqno
  * @tx_rpdupack:             dupacks since rpseq
+ * @tx_av_chunks:            list of Ack Vectors received on current skb
  */
 struct ccid2_hc_tx_sock {
         u32                     tx_cwnd;
@@ -79,6 +80,7 @@ struct ccid2_hc_tx_sock {
         int                     tx_rpdupack;
         u32                     tx_last_cong;
         u64                     tx_high_ack;
+        struct list_head        tx_av_chunks;
 };
 
 static inline bool ccid2_cwnd_network_limited(struct ccid2_hc_tx_sock *hc)
diff --git a/net/dccp/options.c b/net/dccp/options.c
index dabd6ee34d45..f06ffcfc8d71 100644
--- a/net/dccp/options.c
+++ b/net/dccp/options.c
@@ -128,13 +128,6 @@ int dccp_parse_options(struct sock *sk, struct dccp_request_sock *dreq,
                         if (rc)
                                 goto out_featneg_failed;
                         break;
-                case DCCPO_ACK_VECTOR_0:
-                case DCCPO_ACK_VECTOR_1:
-                        if (dccp_packet_without_ack(skb))   /* RFC 4340, 11.4 */
-                                break;
-                        dccp_pr_debug("%s Ack Vector (len=%u)\n", dccp_role(sk),
-                                      len);
-                        break;
                 case DCCPO_TIMESTAMP:
                         if (len != 4)
                                 goto out_invalid_option;
@@ -224,6 +217,16 @@ int dccp_parse_options(struct sock *sk, struct dccp_request_sock *dreq,
                                                      pkt_type, opt, value, len))
                                 goto out_invalid_option;
                         break;
+                case DCCPO_ACK_VECTOR_0:
+                case DCCPO_ACK_VECTOR_1:
+                        if (dccp_packet_without_ack(skb))   /* RFC 4340, 11.4 */
+                                break;
+                        /*
+                         * Ack vectors are processed by the TX CCID if it is
+                         * interested. The RX CCID need not parse Ack Vectors,
+                         * since it is only interested in clearing old state.
+                         * Fall through.
+                         */
                 case DCCPO_MIN_TX_CCID_SPECIFIC ... DCCPO_MAX_TX_CCID_SPECIFIC:
                         if (ccid_hc_tx_parse_options(dp->dccps_hc_tx_ccid, sk,
                                                      pkt_type, opt, value, len))