diff options
| -rw-r--r-- | net/ipv4/tcp_output.c | 23 |
1 files changed, 17 insertions, 6 deletions
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c index de54f02f10a..e4c5ac9fe89 100644 --- a/net/ipv4/tcp_output.c +++ b/net/ipv4/tcp_output.c @@ -362,6 +362,17 @@ struct tcp_out_options { __u32 tsval, tsecr; /* need to include OPTION_TS */ }; +/* Beware: Something in the Internet is very sensitive to the ordering of + * TCP options, we learned this through the hard way, so be careful here. + * Luckily we can at least blame others for their non-compliance but from + * inter-operatibility perspective it seems that we're somewhat stuck with + * the ordering which we have been using if we want to keep working with + * those broken things (not that it currently hurts anybody as there isn't + * particular reason why the ordering would need to be changed). + * + * At least SACK_PERM as the first option is known to lead to a disaster + * (but it may well be that other scenarios fail similarly). + */ static void tcp_options_write(__be32 *ptr, struct tcp_sock *tp, const struct tcp_out_options *opts, __u8 **md5_hash) { @@ -376,6 +387,12 @@ static void tcp_options_write(__be32 *ptr, struct tcp_sock *tp, *md5_hash = NULL; } + if (unlikely(opts->mss)) { + *ptr++ = htonl((TCPOPT_MSS << 24) | + (TCPOLEN_MSS << 16) | + opts->mss); + } + if (likely(OPTION_TS & opts->options)) { if (unlikely(OPTION_SACK_ADVERTISE & opts->options)) { *ptr++ = htonl((TCPOPT_SACK_PERM << 24) | @@ -392,12 +409,6 @@ static void tcp_options_write(__be32 *ptr, struct tcp_sock *tp, *ptr++ = htonl(opts->tsecr); } - if (unlikely(opts->mss)) { - *ptr++ = htonl((TCPOPT_MSS << 24) | - (TCPOLEN_MSS << 16) | - opts->mss); - } - if (unlikely(OPTION_SACK_ADVERTISE & opts->options && !(OPTION_TS & opts->options))) { *ptr++ = htonl((TCPOPT_NOP << 24) | |