[DCCP]: Retrieve packet sequence number for error reporting

This fixes a problem when analysing erroneous packets in dccp_v{4,6}_err:
* dccp_hdr_seq currently takes an skb
* however, the transport headers in the skb are shifted, due to the
  preceding IPv4/v6 header.
Fixed for v4 and v6 by changing dccp_hdr_seq to take a struct dccp_hdr as
argument. Verified that the correct sequence number is now reported in the
error handler.

Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Acked-by: Ian McDonald <ian.mcdonald@jandi.co.nz>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

3 files changed, 8 insertions, 10 deletions

diff --git a/include/linux/dccp.h b/include/linux/dccp.h
index f3fc4392e93d..55d28cb97596 100644
--- a/include/linux/dccp.h
+++ b/include/linux/dccp.h
@@ -270,10 +270,9 @@ static inline struct dccp_hdr *dccp_zeroed_hdr(struct sk_buff *skb, int headlen)
         return memset(skb_transport_header(skb), 0, headlen);
 }
 
-static inline struct dccp_hdr_ext *dccp_hdrx(const struct sk_buff *skb)
+static inline struct dccp_hdr_ext *dccp_hdrx(const struct dccp_hdr *dh)
 {
-        return (struct dccp_hdr_ext *)(skb_transport_header(skb) +
-                                       sizeof(struct dccp_hdr));
+        return (struct dccp_hdr_ext *)((unsigned char *)dh + sizeof(*dh));
 }
 
 static inline unsigned int __dccp_basic_hdr_len(const struct dccp_hdr *dh)
@@ -287,13 +286,12 @@ static inline unsigned int dccp_basic_hdr_len(const struct sk_buff *skb)
         return __dccp_basic_hdr_len(dh);
 }
 
-static inline __u64 dccp_hdr_seq(const struct sk_buff *skb)
+static inline __u64 dccp_hdr_seq(const struct dccp_hdr *dh)
 {
-        const struct dccp_hdr *dh = dccp_hdr(skb);
         __u64 seq_nr =  ntohs(dh->dccph_seq);
 
         if (dh->dccph_x != 0)
-                seq_nr = (seq_nr << 32) + ntohl(dccp_hdrx(skb)->dccph_seq_low);
+                seq_nr = (seq_nr << 32) + ntohl(dccp_hdrx(dh)->dccph_seq_low);
         else
                 seq_nr += (u32)dh->dccph_seq2 << 16;
 
diff --git a/net/dccp/ipv4.c b/net/dccp/ipv4.c
index 222549ab274a..3f1578db93e8 100644
--- a/net/dccp/ipv4.c
+++ b/net/dccp/ipv4.c
@@ -241,7 +241,7 @@ static void dccp_v4_err(struct sk_buff *skb, u32 info)
                 goto out;
 
         dp = dccp_sk(sk);
-        seq = dccp_hdr_seq(skb);
+        seq = dccp_hdr_seq(dh);
         if (sk->sk_state != DCCP_LISTEN &&
             !between48(seq, dp->dccps_swl, dp->dccps_swh)) {
                 NET_INC_STATS_BH(LINUX_MIB_OUTOFWINDOWICMPS);
@@ -795,7 +795,7 @@ static int dccp_v4_rcv(struct sk_buff *skb)
 
         dh = dccp_hdr(skb);
 
-        DCCP_SKB_CB(skb)->dccpd_seq  = dccp_hdr_seq(skb);
+        DCCP_SKB_CB(skb)->dccpd_seq  = dccp_hdr_seq(dh);
         DCCP_SKB_CB(skb)->dccpd_type = dh->dccph_type;
 
         dccp_pr_debug("%8.8s "
diff --git a/net/dccp/ipv6.c b/net/dccp/ipv6.c
index bbadd6681b83..62428ff137dd 100644
--- a/net/dccp/ipv6.c
+++ b/net/dccp/ipv6.c
@@ -173,7 +173,7 @@ static void dccp_v6_err(struct sk_buff *skb, struct inet6_skb_parm *opt,
 
         icmpv6_err_convert(type, code, &err);
 
-        seq = DCCP_SKB_CB(skb)->dccpd_seq;
+        seq = dccp_hdr_seq(dh);
         /* Might be for an request_sock */
         switch (sk->sk_state) {
                 struct request_sock *req, **prev;
@@ -787,7 +787,7 @@ static int dccp_v6_rcv(struct sk_buff *skb)
 
         dh = dccp_hdr(skb);
 
-        DCCP_SKB_CB(skb)->dccpd_seq  = dccp_hdr_seq(skb);
+        DCCP_SKB_CB(skb)->dccpd_seq  = dccp_hdr_seq(dh);
         DCCP_SKB_CB(skb)->dccpd_type = dh->dccph_type;
 
         if (dccp_packet_without_ack(skb))