From 435cf559f02ea3a3159eb316f97dc88bdebe9432 Mon Sep 17 00:00:00 2001 From: William Allen Simpson Date: Wed, 2 Dec 2009 18:17:05 +0000 Subject: TCPCT part 1d: define TCP cookie option, extend existing struct's Data structures are carefully composed to require minimal additions. For example, the struct tcp_options_received cookie_plus variable fits between existing 16-bit and 8-bit variables, requiring no additional space (taking alignment into consideration). There are no additions to tcp_request_sock, and only 1 pointer in tcp_sock. This is a significantly revised implementation of an earlier (year-old) patch that no longer applies cleanly, with permission of the original author (Adam Langley): http://thread.gmane.org/gmane.linux.network/102586 The principle difference is using a TCP option to carry the cookie nonce, instead of a user configured offset in the data. This is more flexible and less subject to user configuration error. Such a cookie option has been suggested for many years, and is also useful without SYN data, allowing several related concepts to use the same extension option. "Re: SYN floods (was: does history repeat itself?)", September 9, 1996. http://www.merit.net/mail.archives/nanog/1996-09/msg00235.html "Re: what a new TCP header might look like", May 12, 1998. ftp://ftp.isi.edu/end2end/end2end-interest-1998.mail These functions will also be used in subsequent patches that implement additional features. Requires: TCPCT part 1a: add request_values parameter for sending SYNACK TCPCT part 1b: generate Responder Cookie secret TCPCT part 1c: sysctl_tcp_cookie_size, socket option TCP_COOKIE_TRANSACTIONS Signed-off-by: William.Allen.Simpson@gmail.com Signed-off-by: David S. Miller --- include/linux/tcp.h | 29 +++++++++++++++++++++++------ 1 file changed, 23 insertions(+), 6 deletions(-) (limited to 'include/linux/tcp.h') diff --git a/include/linux/tcp.h b/include/linux/tcp.h index eaa3113..7fee8a4 100644 --- a/include/linux/tcp.h +++ b/include/linux/tcp.h @@ -247,31 +247,38 @@ struct tcp_options_received { sack_ok : 4, /* SACK seen on SYN packet */ snd_wscale : 4, /* Window scaling received from sender */ rcv_wscale : 4; /* Window scaling to send to receiver */ -/* SACKs data */ + u8 cookie_plus:6, /* bytes in authenticator/cookie option */ + cookie_out_never:1, + cookie_in_always:1; u8 num_sacks; /* Number of SACK blocks */ - u16 user_mss; /* mss requested by user in ioctl */ + u16 user_mss; /* mss requested by user in ioctl */ u16 mss_clamp; /* Maximal mss, negotiated at connection setup */ }; static inline void tcp_clear_options(struct tcp_options_received *rx_opt) { - rx_opt->tstamp_ok = rx_opt->sack_ok = rx_opt->wscale_ok = rx_opt->snd_wscale = 0; + rx_opt->tstamp_ok = rx_opt->sack_ok = 0; + rx_opt->wscale_ok = rx_opt->snd_wscale = 0; + rx_opt->cookie_plus = 0; } /* This is the max number of SACKS that we'll generate and process. It's safe - * to increse this, although since: + * to increase this, although since: * size = TCPOLEN_SACK_BASE_ALIGNED (4) + n * TCPOLEN_SACK_PERBLOCK (8) * only four options will fit in a standard TCP header */ #define TCP_NUM_SACKS 4 +struct tcp_cookie_values; +struct tcp_request_sock_ops; + struct tcp_request_sock { struct inet_request_sock req; #ifdef CONFIG_TCP_MD5SIG /* Only used by TCP MD5 Signature so far. */ const struct tcp_request_sock_ops *af_specific; #endif - u32 rcv_isn; - u32 snt_isn; + u32 rcv_isn; + u32 snt_isn; }; static inline struct tcp_request_sock *tcp_rsk(const struct request_sock *req) @@ -441,6 +448,12 @@ struct tcp_sock { /* TCP MD5 Signature Option information */ struct tcp_md5sig_info *md5sig_info; #endif + + /* When the cookie options are generated and exchanged, then this + * object holds a reference to them (cookie_values->kref). Also + * contains related tcp_cookie_transactions fields. + */ + struct tcp_cookie_values *cookie_values; }; static inline struct tcp_sock *tcp_sk(const struct sock *sk) @@ -459,6 +472,10 @@ struct tcp_timewait_sock { u16 tw_md5_keylen; u8 tw_md5_key[TCP_MD5SIG_MAXKEYLEN]; #endif + /* Few sockets in timewait have cookies; in that case, then this + * object holds a reference to them (tw_cookie_values->kref). + */ + struct tcp_cookie_values *tw_cookie_values; }; static inline struct tcp_timewait_sock *tcp_twsk(const struct sock *sk) -- cgit v1.1