| Message ID | 1276464875-4460-1-git-send-email-fw@strlen.de |
|---|---|
| State | Superseded, archived |
| Delegated to: | David Miller |
| Headers | show |
From: Florian Westphal <fw@strlen.de> Date: Sun, 13 Jun 2010 23:34:35 +0200 > - if (tcp_opt->sack_ok) > - tcp_sack_reset(tcp_opt); > + if (tcp_opt->sack_ok && !sysctl_tcp_sack) > + return false; > If you remove the tcp_sack_reset() call here, who is going to do it? -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
David Miller <davem@davemloft.net> wrote: > From: Florian Westphal <fw@strlen.de> > Date: Sun, 13 Jun 2010 23:34:35 +0200 > > > - if (tcp_opt->sack_ok) > > - tcp_sack_reset(tcp_opt); > > + if (tcp_opt->sack_ok && !sysctl_tcp_sack) > > + return false; > > > > If you remove the tcp_sack_reset() call here, who is going to > do it? Right, I should have mentioned that in the changelog, sorry about that. Bottom line is that I failed to find out why its needed. Both call sites of this function (cookie_v4_check, cookie_v6_check) allocate the "struct tcp_options_received" argument on the stack, zero it, hand it to tcp_parse_options() and then call cookie_check_timestamp(). I did not find any place in tcp_parse_options that would cause tcp_opt->num_sacks/dsack to become nonzero. Even if it can turn nonzero, I do not see any ill effects that might happen then. The structure is on the stack and after tcp_parse_options() returns only a few selected members are copied to the inet_request_sock. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
From: Florian Westphal <fw@strlen.de> Date: Wed, 16 Jun 2010 10:03:09 +0200 > David Miller <davem@davemloft.net> wrote: >> From: Florian Westphal <fw@strlen.de> >> Date: Sun, 13 Jun 2010 23:34:35 +0200 >> >> > - if (tcp_opt->sack_ok) >> > - tcp_sack_reset(tcp_opt); >> > + if (tcp_opt->sack_ok && !sysctl_tcp_sack) >> > + return false; >> > >> >> If you remove the tcp_sack_reset() call here, who is going to >> do it? > > Right, I should have mentioned that in the changelog, sorry about that. > > Bottom line is that I failed to find out why its needed. > Both call sites of this function (cookie_v4_check, cookie_v6_check) > allocate the "struct tcp_options_received" argument on the stack, zero it, > hand it to tcp_parse_options() and then call cookie_check_timestamp(). > > I did not find any place in tcp_parse_options that would cause > tcp_opt->num_sacks/dsack to become nonzero. > > Even if it can turn nonzero, I do not see any ill effects that might > happen then. The structure is on the stack and after tcp_parse_options() > returns only a few selected members are copied to the inet_request_sock. Please resubmit your patch with these explanations in the commit message. Thank you. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/include/net/tcp.h b/include/net/tcp.h index 5731664..cca040e 100644 --- a/include/net/tcp.h +++ b/include/net/tcp.h @@ -464,7 +464,7 @@ extern __u32 cookie_v4_init_sequence(struct sock *sk, struct sk_buff *skb, __u16 *mss); extern __u32 cookie_init_timestamp(struct request_sock *req); -extern void cookie_check_timestamp(struct tcp_options_received *tcp_opt); +extern bool cookie_check_timestamp(struct tcp_options_received *tcp_opt); /* From net/ipv6/syncookies.c */ extern struct sock *cookie_v6_check(struct sock *sk, struct sk_buff *skb); diff --git a/net/ipv4/syncookies.c b/net/ipv4/syncookies.c index 02bef6a..51b5662 100644 --- a/net/ipv4/syncookies.c +++ b/net/ipv4/syncookies.c @@ -230,23 +230,36 @@ static inline struct sock *get_cookie_sock(struct sock *sk, struct sk_buff *skb, * The lowest 4 bits are for snd_wscale * The next 4 lsb are for rcv_wscale * The next lsb is for sack_ok + * + * return false if we decode an option that should not be. */ -void cookie_check_timestamp(struct tcp_options_received *tcp_opt) +bool cookie_check_timestamp(struct tcp_options_received *tcp_opt) { /* echoed timestamp, 9 lowest bits contain options */ u32 options = tcp_opt->rcv_tsecr & TSMASK; + if (!tcp_opt->saw_tstamp) { + tcp_clear_options(tcp_opt); + return true; + } + + if (!sysctl_tcp_timestamps) + return false; + tcp_opt->snd_wscale = options & 0xf; options >>= 4; tcp_opt->rcv_wscale = options & 0xf; tcp_opt->sack_ok = (options >> 4) & 0x1; - if (tcp_opt->sack_ok) - tcp_sack_reset(tcp_opt); + if (tcp_opt->sack_ok && !sysctl_tcp_sack) + return false; - if (tcp_opt->snd_wscale || tcp_opt->rcv_wscale) + if (tcp_opt->snd_wscale || tcp_opt->rcv_wscale) { tcp_opt->wscale_ok = 1; + return sysctl_tcp_window_scaling != 0; + } + return true; } EXPORT_SYMBOL(cookie_check_timestamp); @@ -281,8 +294,8 @@ struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb, memset(&tcp_opt, 0, sizeof(tcp_opt)); tcp_parse_options(skb, &tcp_opt, &hash_location, 0); - if (tcp_opt.saw_tstamp) - cookie_check_timestamp(&tcp_opt); + if (!cookie_check_timestamp(&tcp_opt)) + goto out; ret = NULL; req = inet_reqsk_alloc(&tcp_request_sock_ops); /* for safety */ diff --git a/net/ipv6/syncookies.c b/net/ipv6/syncookies.c index 70d330f..c7ee574 100644 --- a/net/ipv6/syncookies.c +++ b/net/ipv6/syncookies.c @@ -180,8 +180,8 @@ struct sock *cookie_v6_check(struct sock *sk, struct sk_buff *skb) memset(&tcp_opt, 0, sizeof(tcp_opt)); tcp_parse_options(skb, &tcp_opt, &hash_location, 0); - if (tcp_opt.saw_tstamp) - cookie_check_timestamp(&tcp_opt); + if (!cookie_check_timestamp(&tcp_opt)) + goto out; ret = NULL; req = inet6_reqsk_alloc(&tcp6_request_sock_ops);
Discard the ACK if we find options that do not match current sysctl settings. Previously it was possible to create a connection with sack, wscale, etc. enabled even if the feature was disabled via sysctl. Signed-off-by: Florian Westphal <fw@strlen.de> --- include/net/tcp.h | 2 +- net/ipv4/syncookies.c | 25 +++++++++++++++++++------ net/ipv6/syncookies.c | 4 ++-- 3 files changed, 22 insertions(+), 9 deletions(-)