[DCCP]: Factor out common code for generating Resets

This factors code common to dccp_v{4,6}_ctl_send_reset into a separate function,
and adds support for filling in the Data 1 ... Data 3 fields from RFC 4340, 5.6.

It is useful to have this separate, since the following Reset codes will always
be generated from the control socket rather than via dccp_send_reset:
 * Code 3, "No Connection", cf. 8.3.1;
 * Code 4, "Packet Error" (identification for Data 1 added);
 * Code 5, "Option Error" (identification for Data 1..3 added, will be used later);
 * Code 6, "Mandatory Error" (same as Option Error);
 * Code 7, "Connection Refused" (what on Earth is the difference to "No Connection"?);
 * Code 8, "Bad Service Code";
 * Code 9, "Too Busy";
 * Code 10, "Bad Init Cookie" (not used).

Code 0 is not recommended by the RFC, the following codes would be used in
dccp_send_reset() instead, since they all relate to an established DCCP connection:
 * Code 1, "Closed";
 * Code 2, "Aborted";
 * Code 11, "Aggression Penalty" (12.3).

Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Signed-off-by: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>

diff --git a/net/dccp/dccp.h b/net/dccp/dccp.h
index a602d92..ee97950 100644 (file)
--- a/net/dccp/dccp.h
+++ b/net/dccp/dccp.h
@@ -294,6 +294,8 @@ extern unsigned int dccp_poll(struct file *file, struct socket *sock,
 extern int        dccp_v4_connect(struct sock *sk, struct sockaddr *uaddr,
                                   int addr_len);
 
+extern struct sk_buff *dccp_ctl_make_reset(struct socket *ctl,
+                                          struct sk_buff *skb);
 extern int        dccp_send_reset(struct sock *sk, enum dccp_reset_codes code);
 extern void       dccp_send_close(struct sock *sk, const int active);
 extern int        dccp_invalid_packet(struct sk_buff *skb);

diff --git a/net/dccp/ipv4.c b/net/dccp/ipv4.c
index 58a79c2..2312b9f 100644 (file)
--- a/net/dccp/ipv4.c
+++ b/net/dccp/ipv4.c
@@ -510,17 +510,12 @@ out:
 static void dccp_v4_ctl_send_reset(struct sock *sk, struct sk_buff *rxskb)
 {
        int err;
-       struct dccp_hdr *rxdh = dccp_hdr(rxskb), *dh;
        const struct iphdr *rxiph;
-       const int dccp_hdr_reset_len = sizeof(struct dccp_hdr) +
-                                      sizeof(struct dccp_hdr_ext) +
-                                      sizeof(struct dccp_hdr_reset);
        struct sk_buff *skb;
        struct dst_entry *dst;
-       u64 seqno = 0;
 
        /* Never send a reset in response to a reset. */
-       if (rxdh->dccph_type == DCCP_PKT_RESET)
+       if (dccp_hdr(rxskb)->dccph_type == DCCP_PKT_RESET)
                return;
 
        if (((struct rtable *)rxskb->dst)->rt_type != RTN_LOCAL)
@@ -530,37 +525,14 @@ static void dccp_v4_ctl_send_reset(struct sock *sk, struct sk_buff *rxskb)
        if (dst == NULL)
                return;
 
-       skb = alloc_skb(dccp_v4_ctl_socket->sk->sk_prot->max_header,
-                       GFP_ATOMIC);
+       skb = dccp_ctl_make_reset(dccp_v4_ctl_socket, rxskb);
        if (skb == NULL)
                goto out;
 
-       /* Reserve space for headers. */
-       skb_reserve(skb, dccp_v4_ctl_socket->sk->sk_prot->max_header);
-       skb->dst = dst_clone(dst);
-
-       dh = dccp_zeroed_hdr(skb, dccp_hdr_reset_len);
-
-       /* Build DCCP header and checksum it. */
-       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;
-       dccp_hdr_reset(skb)->dccph_reset_code =
-                               DCCP_SKB_CB(rxskb)->dccpd_reset_code;
-
-       /* See "8.3.1. Abnormal Termination" in RFC 4340 */
-       if (DCCP_SKB_CB(rxskb)->dccpd_ack_seq != DCCP_PKT_WITHOUT_ACK_SEQ)
-               seqno = ADD48(DCCP_SKB_CB(rxskb)->dccpd_ack_seq, 1);
-
-       dccp_hdr_set_seq(dh, seqno);
-       dccp_hdr_set_ack(dccp_hdr_ack_bits(skb), DCCP_SKB_CB(rxskb)->dccpd_seq);
-
-       dccp_csum_outgoing(skb);
        rxiph = ip_hdr(rxskb);
-       dh->dccph_checksum = dccp_v4_csum_finish(skb, rxiph->saddr,
-                                                rxiph->daddr);
+       dccp_hdr(skb)->dccph_checksum = dccp_v4_csum_finish(skb, rxiph->saddr,
+                                                                rxiph->daddr);
+       skb->dst = dst_clone(dst);
 
        bh_lock_sock(dccp_v4_ctl_socket->sk);
        err = ip_build_and_send_pkt(skb, dccp_v4_ctl_socket->sk,

diff --git a/net/dccp/ipv6.c b/net/dccp/ipv6.c
index d954e83..b7c0f66 100644 (file)
--- a/net/dccp/ipv6.c
+++ b/net/dccp/ipv6.c
@@ -301,50 +301,23 @@ static void dccp_v6_reqsk_destructor(struct request_sock *req)
 
 static void dccp_v6_ctl_send_reset(struct sock *sk, struct sk_buff *rxskb)
 {
-       struct dccp_hdr *rxdh = dccp_hdr(rxskb), *dh;
        struct ipv6hdr *rxip6h;
-       const u32 dccp_hdr_reset_len = sizeof(struct dccp_hdr) +
-                                      sizeof(struct dccp_hdr_ext) +
-                                      sizeof(struct dccp_hdr_reset);
        struct sk_buff *skb;
        struct flowi fl;
-       u64 seqno = 0;
 
-       if (rxdh->dccph_type == DCCP_PKT_RESET)
+       if (dccp_hdr(rxskb)->dccph_type == DCCP_PKT_RESET)
                return;
 
        if (!ipv6_unicast_destination(rxskb))
                return;
 
-       skb = alloc_skb(dccp_v6_ctl_socket->sk->sk_prot->max_header,
-                       GFP_ATOMIC);
+       skb = dccp_ctl_make_reset(dccp_v6_ctl_socket, rxskb);
        if (skb == NULL)
                return;
 
-       skb_reserve(skb, dccp_v6_ctl_socket->sk->sk_prot->max_header);
-
-       dh = dccp_zeroed_hdr(skb, dccp_hdr_reset_len);
-
-       /* Swap the send and the receive. */
-       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;
-       dccp_hdr_reset(skb)->dccph_reset_code =
-                               DCCP_SKB_CB(rxskb)->dccpd_reset_code;
-
-       /* See "8.3.1. Abnormal Termination" in RFC 4340 */
-       if (DCCP_SKB_CB(rxskb)->dccpd_ack_seq != DCCP_PKT_WITHOUT_ACK_SEQ)
-               seqno = ADD48(DCCP_SKB_CB(rxskb)->dccpd_ack_seq, 1);
-
-       dccp_hdr_set_seq(dh, seqno);
-       dccp_hdr_set_ack(dccp_hdr_ack_bits(skb), DCCP_SKB_CB(rxskb)->dccpd_seq);
-
-       dccp_csum_outgoing(skb);
        rxip6h = ipv6_hdr(rxskb);
-       dh->dccph_checksum = dccp_v6_csum_finish(skb, &rxip6h->saddr,
-                                                     &rxip6h->daddr);
+       dccp_hdr(skb)->dccph_checksum = dccp_v6_csum_finish(skb, &rxip6h->saddr,
+                                                           &rxip6h->daddr);
 
        memset(&fl, 0, sizeof(fl));
        ipv6_addr_copy(&fl.fl6_dst, &rxip6h->saddr);
@@ -352,8 +325,8 @@ static void dccp_v6_ctl_send_reset(struct sock *sk, struct sk_buff *rxskb)
 
        fl.proto = IPPROTO_DCCP;
        fl.oif = inet6_iif(rxskb);
-       fl.fl_ip_dport = dh->dccph_dport;
-       fl.fl_ip_sport = dh->dccph_sport;
+       fl.fl_ip_dport = dccp_hdr(skb)->dccph_dport;
+       fl.fl_ip_sport = dccp_hdr(skb)->dccph_sport;
        security_skb_classify_flow(rxskb, &fl);
 
        /* sk = NULL, but it is safe for now. RST socket required. */

diff --git a/net/dccp/output.c b/net/dccp/output.c
index f4bde20..6a334ed 100644 (file)
--- a/net/dccp/output.c
+++ b/net/dccp/output.c
@@ -327,6 +327,58 @@ struct sk_buff *dccp_make_response(struct sock *sk, struct dst_entry *dst,
 
 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 socket *ctl, 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(ctl->sk->sk_prot->max_header, GFP_ATOMIC);
+       if (skb == NULL)
+               return NULL;
+
+       skb_reserve(skb, ctl->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)
 {