3 files changed, 28 insertions, 22 deletions

diff --git a/net/dccp/dccp.h b/net/dccp/dccp.h
index fb83454102c1..55b690ab61ae 100644
--- a/net/dccp/dccp.h
+++ b/net/dccp/dccp.h
@@ -242,7 +242,8 @@ extern int	   dccp_setsockopt(struct sock *sk, int level, int optname,
                                    char *optval, int optlen);
 extern void        dccp_shutdown(struct sock *sk, int how);
 
-extern int         dccp_v4_checksum(struct sk_buff *skb);
+extern int         dccp_v4_checksum(const struct sk_buff *skb,
+                                    const u32 saddr, const u32 daddr);
 
 extern int         dccp_v4_send_reset(struct sock *sk, enum dccp_reset_codes code);
 extern void        dccp_send_close(struct sock *sk);
diff --git a/net/dccp/ipv4.c b/net/dccp/ipv4.c
index 083bacaecb3b..7b90606ec10e 100644
--- a/net/dccp/ipv4.c
+++ b/net/dccp/ipv4.c
@@ -802,9 +802,9 @@ static struct sock *dccp_v4_hnd_req(struct sock *sk, struct sk_buff *skb)
         return sk;
 }
 
-int dccp_v4_checksum(struct sk_buff *skb)
+int dccp_v4_checksum(const struct sk_buff *skb, const u32 saddr, const u32 daddr)
 {
-        struct dccp_hdr* dh = dccp_hdr(skb);
+        const struct dccp_hdr* dh = dccp_hdr(skb);
         int checksum_len;
         u32 tmp;
 
@@ -816,24 +816,24 @@ int dccp_v4_checksum(struct sk_buff *skb)
         }
 
         tmp = csum_partial((unsigned char *)dh, checksum_len, 0);
-        return csum_fold(tmp);
+        return csum_tcpudp_magic(saddr, daddr, checksum_len, IPPROTO_DCCP, tmp);
 }
 
-static int dccp_v4_verify_checksum(struct sk_buff *skb)
+static int dccp_v4_verify_checksum(struct sk_buff *skb,
+                                   const u32 saddr, const u32 daddr)
 {
-        struct dccp_hdr *th = dccp_hdr(skb);
-        const u16 remote_checksum = th->dccph_checksum;
-        u16 local_checksum;
-
-        /* FIXME: don't mess with skb payload */
-        th->dccph_checksum = 0; /* zero it for computation */
-
-        local_checksum = dccp_v4_checksum(skb);
-
-        /* FIXME: don't mess with skb payload */
-        th->dccph_checksum = remote_checksum; /* put it back */
+        struct dccp_hdr *dh = dccp_hdr(skb);
+        int checksum_len;
+        u32 tmp;
 
-        return remote_checksum == local_checksum ? 0 : -1;
+        if (dh->dccph_cscov == 0)
+                checksum_len = skb->len;
+        else {
+                checksum_len = (dh->dccph_cscov + dh->dccph_x) * sizeof(u32);
+                checksum_len = checksum_len < skb->len ? checksum_len : skb->len;
+        }
+        tmp = csum_partial((unsigned char *)dh, checksum_len, 0);
+        return csum_tcpudp_magic(saddr, daddr, checksum_len, IPPROTO_DCCP, tmp) == 0 ? 0 : -1;
 }
 
 static struct dst_entry* dccp_v4_route_skb(struct sock *sk,
@@ -902,7 +902,8 @@ void dccp_v4_ctl_send_reset(struct sk_buff *rxskb)
         dccp_hdr_set_seq(dh, DCCP_SKB_CB(rxskb)->dccpd_ack_seq);
         dccp_hdr_set_ack(dccp_hdr_ack_bits(skb), DCCP_SKB_CB(rxskb)->dccpd_seq);
 
-        dh->dccph_checksum = dccp_v4_checksum(skb);
+        dh->dccph_checksum = dccp_v4_checksum(skb, rxskb->nh.iph->saddr,
+                                              rxskb->nh.iph->daddr);
 
         bh_lock_sock(dccp_ctl_socket->sk);
         err = ip_build_and_send_pkt(skb, dccp_ctl_socket->sk,
@@ -1024,7 +1025,8 @@ static inline int dccp_invalid_packet(struct sk_buff *skb)
         }
 
         /* If the header checksum is incorrect, drop packet and return */
-        if (dccp_v4_verify_checksum(skb) < 0) {
+        if (dccp_v4_verify_checksum(skb, skb->nh.iph->saddr,
+                                    skb->nh.iph->daddr) < 0) {
                 dccp_pr_debug("header checksum is incorrect\n");
                 return 1;
         }
diff --git a/net/dccp/output.c b/net/dccp/output.c
index 22ca2910d4f2..4945eaa9d1a4 100644
--- a/net/dccp/output.c
+++ b/net/dccp/output.c
@@ -93,7 +93,8 @@ int dccp_transmit_skb(struct sock *sk, struct sk_buff *skb)
                         break;
                 }
 
-                dh->dccph_checksum = dccp_v4_checksum(skb);
+                dh->dccph_checksum = dccp_v4_checksum(skb, inet->saddr,
+                                                      inet->daddr);
 
                 if (dcb->dccpd_type == DCCP_PKT_ACK ||
                     dcb->dccpd_type == DCCP_PKT_DATAACK)
@@ -193,7 +194,8 @@ struct sk_buff *dccp_make_response(struct sock *sk, struct dst_entry *dst,
         dccp_hdr_set_seq(dh, dccp_rsk(req)->dreq_iss);
         dccp_hdr_set_ack(dccp_hdr_ack_bits(skb), dccp_rsk(req)->dreq_isr);
 
-        dh->dccph_checksum = dccp_v4_checksum(skb);
+        dh->dccph_checksum = dccp_v4_checksum(skb, inet_rsk(req)->loc_addr,
+                                              inet_rsk(req)->rmt_addr);
 
         DCCP_INC_STATS(DCCP_MIB_OUTSEGS);
         return skb;
@@ -242,7 +244,8 @@ struct sk_buff *dccp_make_reset(struct sock *sk, struct dst_entry *dst,
 
         dccp_hdr_reset(skb)->dccph_reset_code = code;
 
-        dh->dccph_checksum = dccp_v4_checksum(skb);
+        dh->dccph_checksum = dccp_v4_checksum(skb, inet_sk(sk)->saddr,
+                                              inet_sk(sk)->daddr);
 
         DCCP_INC_STATS(DCCP_MIB_OUTSEGS);
         return skb;