diff options
| -rw-r--r-- | Documentation/networking/ip-sysctl.txt | 5 | ||||
| -rw-r--r-- | include/linux/snmp.h | 1 | ||||
| -rw-r--r-- | include/net/tcp.h | 1 | ||||
| -rw-r--r-- | net/ipv4/proc.c | 1 | ||||
| -rw-r--r-- | net/ipv4/sysctl_net_ipv4.c | 7 | ||||
| -rw-r--r-- | net/ipv4/tcp_input.c | 31 |
6 files changed, 45 insertions, 1 deletions
diff --git a/Documentation/networking/ip-sysctl.txt b/Documentation/networking/ip-sysctl.txt index e20c17a7d34e..e1e021594cff 100644 --- a/Documentation/networking/ip-sysctl.txt +++ b/Documentation/networking/ip-sysctl.txt @@ -565,6 +565,11 @@ tcp_limit_output_bytes - INTEGER reduce the size of individual GSO packet (64KB being the max) Default: 131072 +tcp_challenge_ack_limit - INTEGER + Limits number of Challenge ACK sent per second, as recommended + in RFC 5961 (Improving TCP's Robustness to Blind In-Window Attacks) + Default: 100 + UDP variables: udp_mem - vector of 3 INTEGERs: min, pressure, max diff --git a/include/linux/snmp.h b/include/linux/snmp.h index 6e4c51123828..673e0e928b2b 100644 --- a/include/linux/snmp.h +++ b/include/linux/snmp.h @@ -237,6 +237,7 @@ enum LINUX_MIB_TCPOFOQUEUE, /* TCPOFOQueue */ LINUX_MIB_TCPOFODROP, /* TCPOFODrop */ LINUX_MIB_TCPOFOMERGE, /* TCPOFOMerge */ + LINUX_MIB_TCPCHALLENGEACK, /* TCPChallengeACK */ __LINUX_MIB_MAX }; diff --git a/include/net/tcp.h b/include/net/tcp.h index 439984b9af49..85c5090bfe25 100644 --- a/include/net/tcp.h +++ b/include/net/tcp.h @@ -254,6 +254,7 @@ extern int sysctl_tcp_thin_linear_timeouts; extern int sysctl_tcp_thin_dupack; extern int sysctl_tcp_early_retrans; extern int sysctl_tcp_limit_output_bytes; +extern int sysctl_tcp_challenge_ack_limit; extern atomic_long_t tcp_memory_allocated; extern struct percpu_counter tcp_sockets_allocated; diff --git a/net/ipv4/proc.c b/net/ipv4/proc.c index dae25e7622cf..3e8e78f12a38 100644 --- a/net/ipv4/proc.c +++ b/net/ipv4/proc.c @@ -261,6 +261,7 @@ static const struct snmp_mib snmp4_net_list[] = { SNMP_MIB_ITEM("TCPOFOQueue", LINUX_MIB_TCPOFOQUEUE), SNMP_MIB_ITEM("TCPOFODrop", LINUX_MIB_TCPOFODROP), SNMP_MIB_ITEM("TCPOFOMerge", LINUX_MIB_TCPOFOMERGE), + SNMP_MIB_ITEM("TCPChallengeACK", LINUX_MIB_TCPCHALLENGEACK), SNMP_MIB_SENTINEL }; diff --git a/net/ipv4/sysctl_net_ipv4.c b/net/ipv4/sysctl_net_ipv4.c index 70730f7aeafe..3f6a1e762e9c 100644 --- a/net/ipv4/sysctl_net_ipv4.c +++ b/net/ipv4/sysctl_net_ipv4.c @@ -605,6 +605,13 @@ static struct ctl_table ipv4_table[] = { .mode = 0644, .proc_handler = proc_dointvec }, + { + .procname = "tcp_challenge_ack_limit", + .data = &sysctl_tcp_challenge_ack_limit, + .maxlen = sizeof(int), + .mode = 0644, + .proc_handler = proc_dointvec + }, #ifdef CONFIG_NET_DMA { .procname = "tcp_dma_copybreak", diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c index cc4e12f1f2f7..c841a8990377 100644 --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -88,6 +88,9 @@ int sysctl_tcp_app_win __read_mostly = 31; int sysctl_tcp_adv_win_scale __read_mostly = 1; EXPORT_SYMBOL(sysctl_tcp_adv_win_scale); +/* rfc5961 challenge ack rate limiting */ +int sysctl_tcp_challenge_ack_limit = 100; + int sysctl_tcp_stdurg __read_mostly; int sysctl_tcp_rfc1337 __read_mostly; int sysctl_tcp_max_orphans __read_mostly = NR_FILE; @@ -5247,6 +5250,23 @@ out: } #endif /* CONFIG_NET_DMA */ +static void tcp_send_challenge_ack(struct sock *sk) +{ + /* unprotected vars, we dont care of overwrites */ + static u32 challenge_timestamp; + static unsigned int challenge_count; + u32 now = jiffies / HZ; + + if (now != challenge_timestamp) { + challenge_timestamp = now; + challenge_count = 0; + } + if (++challenge_count <= sysctl_tcp_challenge_ack_limit) { + NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPCHALLENGEACK); + tcp_send_ack(sk); + } +} + /* Does PAWS and seqno based validation of an incoming segment, flags will * play significant role here. */ @@ -5283,7 +5303,16 @@ static int tcp_validate_incoming(struct sock *sk, struct sk_buff *skb, /* Step 2: check RST bit */ if (th->rst) { - tcp_reset(sk); + /* RFC 5961 3.2 : + * If sequence number exactly matches RCV.NXT, then + * RESET the connection + * else + * Send a challenge ACK + */ + if (TCP_SKB_CB(skb)->seq == tp->rcv_nxt) + tcp_reset(sk); + else + tcp_send_challenge_ack(sk); goto discard; } |