tcp: unalias tcp_skb_cb flags and ip_dsfield

struct tcp_skb_cb contains a "flags" field containing either tcp flags
or IP dsfield depending on context (input or output path)

Introduce ip_dsfield to make the difference clear and ease maintenance.
If later we want to save space, we can union flags/ip_dsfield

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

4 files changed, 5 insertions, 4 deletions

diff --git a/include/net/tcp.h b/include/net/tcp.h
index 702aefc8d43d..28a9997d783a 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -642,7 +642,8 @@ struct tcp_skb_cb {
 #define TCPCB_SACKED_RETRANS    0x02    /* SKB retransmitted            */
 #define TCPCB_LOST              0x04    /* SKB is lost                  */
 #define TCPCB_TAGBITS           0x07    /* All tag bits                 */
-
+        __u8            ip_dsfield;     /* IPv4 tos or IPv6 dsfield     */
+        /* 1 byte hole */
 #define TCPCB_EVER_RETRANS      0x80    /* Ever retransmitted frame     */
 #define TCPCB_RETRANS           (TCPCB_SACKED_RETRANS|TCPCB_EVER_RETRANS)
 
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 5a4408c55155..7008fccc164f 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -222,7 +222,7 @@ static inline void TCP_ECN_check_ce(struct tcp_sock *tp, const struct sk_buff *s
         if (!(tp->ecn_flags & TCP_ECN_OK))
                 return;
 
-        switch (TCP_SKB_CB(skb)->flags & INET_ECN_MASK) {
+        switch (TCP_SKB_CB(skb)->ip_dsfield & INET_ECN_MASK) {
         case INET_ECN_NOT_ECT:
                 /* Funny extension: if ECT is not set on a segment,
                  * and we already seen ECT on a previous segment,
diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index c29912cd83a0..dd3fad9fb633 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -1677,7 +1677,7 @@ int tcp_v4_rcv(struct sk_buff *skb)
                                     skb->len - th->doff * 4);
         TCP_SKB_CB(skb)->ack_seq = ntohl(th->ack_seq);
         TCP_SKB_CB(skb)->when    = 0;
-        TCP_SKB_CB(skb)->flags   = iph->tos;
+        TCP_SKB_CB(skb)->ip_dsfield = ipv4_get_dsfield(iph);
         TCP_SKB_CB(skb)->sacked  = 0;
 
         sk = __inet_lookup_skb(&tcp_hashinfo, skb, th->source, th->dest);
diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index 12bdb9af96e5..00797d857667 100644
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -1717,7 +1717,7 @@ static int tcp_v6_rcv(struct sk_buff *skb)
                                     skb->len - th->doff*4);
         TCP_SKB_CB(skb)->ack_seq = ntohl(th->ack_seq);
         TCP_SKB_CB(skb)->when = 0;
-        TCP_SKB_CB(skb)->flags = ipv6_get_dsfield(hdr);
+        TCP_SKB_CB(skb)->ip_dsfield = ipv6_get_dsfield(hdr);
         TCP_SKB_CB(skb)->sacked = 0;
 
         sk = __inet6_lookup_skb(&tcp_hashinfo, skb, th->source, th->dest);