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Diffstat (limited to 'net/ipv4/tcp_bbr.c')
-rw-r--r--net/ipv4/tcp_bbr.c6
1 files changed, 4 insertions, 2 deletions
diff --git a/net/ipv4/tcp_bbr.c b/net/ipv4/tcp_bbr.c
index 56be7d27f208..95b59540eee1 100644
--- a/net/ipv4/tcp_bbr.c
+++ b/net/ipv4/tcp_bbr.c
@@ -346,7 +346,7 @@ static void bbr_cwnd_event(struct sock *sk, enum tcp_ca_event event)
/* Calculate bdp based on min RTT and the estimated bottleneck bandwidth:
*
- * bdp = bw * min_rtt * gain
+ * bdp = ceil(bw * min_rtt * gain)
*
* The key factor, gain, controls the amount of queue. While a small gain
* builds a smaller queue, it becomes more vulnerable to noise in RTT
@@ -370,7 +370,9 @@ static u32 bbr_bdp(struct sock *sk, u32 bw, int gain)
w = (u64)bw * bbr->min_rtt_us;
- /* Apply a gain to the given value, then remove the BW_SCALE shift. */
+ /* Apply a gain to the given value, remove the BW_SCALE shift, and
+ * round the value up to avoid a negative feedback loop.
+ */
bdp = (((w * gain) >> BBR_SCALE) + BW_UNIT - 1) / BW_UNIT;
return bdp;