From: Ilpo Järvinen <i...@kernel.org>
1) Don't early return when sack doesn't fit. AccECN code will be
placed after this fragment so no early returns please.
2) Make sure opts->num_sack_blocks is not left undefined. E.g.,
tcp_current_mss() does not memset its opts struct to zero.
AccECN code checks if SACK option is present and may even
alter it to make room for AccECN option when many SACK blocks
are present. Thus, num_sack_blocks needs to be always valid.
Signed-off-by: Ilpo Järvinen <i...@kernel.org>
Signed-off-by: Chia-Yu Chang <chia-yu.ch...@nokia-bell-labs.com>
Reviewed-by: Eric Dumazet <eduma...@google.com>
---
v8:
- Set opts->num_sack_blocks=0 to avoid potential undefined value
---
net/ipv4/tcp_output.c | 25 ++++++++++++++-----------
1 file changed, 14 insertions(+), 11 deletions(-)
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 44b46569f74e..c093248ce36c 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -985,17 +985,20 @@ static unsigned int tcp_established_options(struct sock
*sk, struct sk_buff *skb
eff_sacks = tp->rx_opt.num_sacks + tp->rx_opt.dsack;
if (unlikely(eff_sacks)) {
const unsigned int remaining = MAX_TCP_OPTION_SPACE - size;
- if (unlikely(remaining < TCPOLEN_SACK_BASE_ALIGNED +
- TCPOLEN_SACK_PERBLOCK))
- return size;
-
- opts->num_sack_blocks =
- min_t(unsigned int, eff_sacks,
- (remaining - TCPOLEN_SACK_BASE_ALIGNED) /
- TCPOLEN_SACK_PERBLOCK);
-
- size += TCPOLEN_SACK_BASE_ALIGNED +
- opts->num_sack_blocks * TCPOLEN_SACK_PERBLOCK;
+ if (likely(remaining >= TCPOLEN_SACK_BASE_ALIGNED +
+ TCPOLEN_SACK_PERBLOCK)) {
+ opts->num_sack_blocks =
+ min_t(unsigned int, eff_sacks,
+ (remaining - TCPOLEN_SACK_BASE_ALIGNED) /
+ TCPOLEN_SACK_PERBLOCK);
+
+ size += TCPOLEN_SACK_BASE_ALIGNED +
+ opts->num_sack_blocks * TCPOLEN_SACK_PERBLOCK;
+ } else {
+ opts->num_sack_blocks = 0;
+ }
+ } else {
+ opts->num_sack_blocks = 0;
}
if (unlikely(BPF_SOCK_OPS_TEST_FLAG(tp,
--
2.34.1
