tcp: Remove redundant checks when setting eff_sacks
Remove redundant checks when setting eff_sacks and make the number of SACKs a
compile time constant. Now that the options code knows how many SACK blocks can
fit in the header, we don't need to have the SACK code guessing at it.
Signed-off-by: Adam Langley <agl@imperialviolet.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/linux/tcp.h b/include/linux/tcp.h
index 07e79bd..2e25573 100644
--- a/include/linux/tcp.h
+++ b/include/linux/tcp.h
@@ -224,6 +224,12 @@
u16 mss_clamp; /* Maximal mss, negotiated at connection setup */
};
+/* This is the max number of SACKS that we'll generate and process. It's safe
+ * to increse this, although since:
+ * size = TCPOLEN_SACK_BASE_ALIGNED (4) + n * TCPOLEN_SACK_PERBLOCK (8)
+ * only four options will fit in a standard TCP header */
+#define TCP_NUM_SACKS 4
+
struct tcp_request_sock {
struct inet_request_sock req;
#ifdef CONFIG_TCP_MD5SIG
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 88810bc..1f5e604 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -1423,10 +1423,10 @@
unsigned char *ptr = (skb_transport_header(ack_skb) +
TCP_SKB_CB(ack_skb)->sacked);
struct tcp_sack_block_wire *sp_wire = (struct tcp_sack_block_wire *)(ptr+2);
- struct tcp_sack_block sp[4];
+ struct tcp_sack_block sp[TCP_NUM_SACKS];
struct tcp_sack_block *cache;
struct sk_buff *skb;
- int num_sacks = (ptr[1] - TCPOLEN_SACK_BASE) >> 3;
+ int num_sacks = min(TCP_NUM_SACKS, (ptr[1] - TCPOLEN_SACK_BASE) >> 3);
int used_sacks;
int reord = tp->packets_out;
int flag = 0;
@@ -3735,8 +3735,7 @@
tp->rx_opt.dsack = 1;
tp->duplicate_sack[0].start_seq = seq;
tp->duplicate_sack[0].end_seq = end_seq;
- tp->rx_opt.eff_sacks = min(tp->rx_opt.num_sacks + 1,
- 4 - tp->rx_opt.tstamp_ok);
+ tp->rx_opt.eff_sacks = tp->rx_opt.num_sacks + 1;
}
}
@@ -3791,9 +3790,8 @@
* Decrease num_sacks.
*/
tp->rx_opt.num_sacks--;
- tp->rx_opt.eff_sacks = min(tp->rx_opt.num_sacks +
- tp->rx_opt.dsack,
- 4 - tp->rx_opt.tstamp_ok);
+ tp->rx_opt.eff_sacks = tp->rx_opt.num_sacks +
+ tp->rx_opt.dsack;
for (i = this_sack; i < tp->rx_opt.num_sacks; i++)
sp[i] = sp[i + 1];
continue;
@@ -3843,7 +3841,7 @@
*
* If the sack array is full, forget about the last one.
*/
- if (this_sack >= 4) {
+ if (this_sack >= TCP_NUM_SACKS) {
this_sack--;
tp->rx_opt.num_sacks--;
sp--;
@@ -3856,8 +3854,7 @@
sp->start_seq = seq;
sp->end_seq = end_seq;
tp->rx_opt.num_sacks++;
- tp->rx_opt.eff_sacks = min(tp->rx_opt.num_sacks + tp->rx_opt.dsack,
- 4 - tp->rx_opt.tstamp_ok);
+ tp->rx_opt.eff_sacks = tp->rx_opt.num_sacks + tp->rx_opt.dsack;
}
/* RCV.NXT advances, some SACKs should be eaten. */
@@ -3894,9 +3891,8 @@
}
if (num_sacks != tp->rx_opt.num_sacks) {
tp->rx_opt.num_sacks = num_sacks;
- tp->rx_opt.eff_sacks = min(tp->rx_opt.num_sacks +
- tp->rx_opt.dsack,
- 4 - tp->rx_opt.tstamp_ok);
+ tp->rx_opt.eff_sacks = tp->rx_opt.num_sacks +
+ tp->rx_opt.dsack;
}
}
@@ -3975,8 +3971,7 @@
if (tp->rx_opt.dsack) {
tp->rx_opt.dsack = 0;
- tp->rx_opt.eff_sacks = min_t(unsigned int, tp->rx_opt.num_sacks,
- 4 - tp->rx_opt.tstamp_ok);
+ tp->rx_opt.eff_sacks = tp->rx_opt.num_sacks;
}
/* Queue data for delivery to the user.