From: Ilpo Järvinen ij@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 ij@kernel.org Signed-off-by: Chia-Yu Chang chia-yu.chang@nokia-bell-labs.com Reviewed-by: Eric Dumazet edumazet@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 debcb1d431e6..d98a1a17eb52 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,