diff options
Diffstat (limited to 'include')
| -rw-r--r-- | include/linux/tcp.h | 6 | ||||
| -rw-r--r-- | include/net/tcp.h | 33 | ||||
| -rw-r--r-- | include/uapi/linux/snmp.h | 6 |
3 files changed, 45 insertions, 0 deletions
diff --git a/include/linux/tcp.h b/include/linux/tcp.h index 67309ece0772..1a7adb411647 100644 --- a/include/linux/tcp.h +++ b/include/linux/tcp.h @@ -115,6 +115,7 @@ struct tcp_request_sock { u32 rcv_isn; u32 snt_isn; u32 snt_synack; /* synack sent time */ + u32 last_oow_ack_time; /* last SYNACK */ u32 rcv_nxt; /* the ack # by SYNACK. For * FastOpen it's the seq# * after data-in-SYN. @@ -152,6 +153,7 @@ struct tcp_sock { u32 snd_sml; /* Last byte of the most recently transmitted small packet */ u32 rcv_tstamp; /* timestamp of last received ACK (for keepalives) */ u32 lsndtime; /* timestamp of last sent data packet (for restart window) */ + u32 last_oow_ack_time; /* timestamp of last out-of-window ACK */ u32 tsoffset; /* timestamp offset */ @@ -340,6 +342,10 @@ struct tcp_timewait_sock { u32 tw_rcv_wnd; u32 tw_ts_offset; u32 tw_ts_recent; + + /* The time we sent the last out-of-window ACK: */ + u32 tw_last_oow_ack_time; + long tw_ts_recent_stamp; #ifdef CONFIG_TCP_MD5SIG struct tcp_md5sig_key *tw_md5_key; diff --git a/include/net/tcp.h b/include/net/tcp.h index 28e9bd3abceb..da4196fb78db 100644 --- a/include/net/tcp.h +++ b/include/net/tcp.h @@ -274,6 +274,7 @@ extern int sysctl_tcp_challenge_ack_limit; extern unsigned int sysctl_tcp_notsent_lowat; extern int sysctl_tcp_min_tso_segs; extern int sysctl_tcp_autocorking; +extern int sysctl_tcp_invalid_ratelimit; extern atomic_long_t tcp_memory_allocated; extern struct percpu_counter tcp_sockets_allocated; @@ -1144,6 +1145,7 @@ static inline void tcp_openreq_init(struct request_sock *req, tcp_rsk(req)->rcv_isn = TCP_SKB_CB(skb)->seq; tcp_rsk(req)->rcv_nxt = TCP_SKB_CB(skb)->seq + 1; tcp_rsk(req)->snt_synack = tcp_time_stamp; + tcp_rsk(req)->last_oow_ack_time = 0; req->mss = rx_opt->mss_clamp; req->ts_recent = rx_opt->saw_tstamp ? rx_opt->rcv_tsval : 0; ireq->tstamp_ok = rx_opt->tstamp_ok; @@ -1236,6 +1238,37 @@ static inline bool tcp_paws_reject(const struct tcp_options_received *rx_opt, return true; } +/* Return true if we're currently rate-limiting out-of-window ACKs and + * thus shouldn't send a dupack right now. We rate-limit dupacks in + * response to out-of-window SYNs or ACKs to mitigate ACK loops or DoS + * attacks that send repeated SYNs or ACKs for the same connection. To + * do this, we do not send a duplicate SYNACK or ACK if the remote + * endpoint is sending out-of-window SYNs or pure ACKs at a high rate. + */ +static inline bool tcp_oow_rate_limited(struct net *net, + const struct sk_buff *skb, + int mib_idx, u32 *last_oow_ack_time) +{ + /* Data packets without SYNs are not likely part of an ACK loop. */ + if ((TCP_SKB_CB(skb)->seq != TCP_SKB_CB(skb)->end_seq) && + !tcp_hdr(skb)->syn) + goto not_rate_limited; + + if (*last_oow_ack_time) { + s32 elapsed = (s32)(tcp_time_stamp - *last_oow_ack_time); + + if (0 <= elapsed && elapsed < sysctl_tcp_invalid_ratelimit) { + NET_INC_STATS_BH(net, mib_idx); + return true; /* rate-limited: don't send yet! */ + } + } + + *last_oow_ack_time = tcp_time_stamp; + +not_rate_limited: + return false; /* not rate-limited: go ahead, send dupack now! */ +} + static inline void tcp_mib_init(struct net *net) { /* See RFC 2012 */ diff --git a/include/uapi/linux/snmp.h b/include/uapi/linux/snmp.h index b22224100011..6a6fb747c78d 100644 --- a/include/uapi/linux/snmp.h +++ b/include/uapi/linux/snmp.h @@ -270,6 +270,12 @@ enum LINUX_MIB_TCPHYSTARTTRAINCWND, /* TCPHystartTrainCwnd */ LINUX_MIB_TCPHYSTARTDELAYDETECT, /* TCPHystartDelayDetect */ LINUX_MIB_TCPHYSTARTDELAYCWND, /* TCPHystartDelayCwnd */ + LINUX_MIB_TCPACKSKIPPEDSYNRECV, /* TCPACKSkippedSynRecv */ + LINUX_MIB_TCPACKSKIPPEDPAWS, /* TCPACKSkippedPAWS */ + LINUX_MIB_TCPACKSKIPPEDSEQ, /* TCPACKSkippedSeq */ + LINUX_MIB_TCPACKSKIPPEDFINWAIT2, /* TCPACKSkippedFinWait2 */ + LINUX_MIB_TCPACKSKIPPEDTIMEWAIT, /* TCPACKSkippedTimeWait */ + LINUX_MIB_TCPACKSKIPPEDCHALLENGE, /* TCPACKSkippedChallenge */ __LINUX_MIB_MAX }; |