Add the ability to limit how much the code will fragment the RACK send map
in response to SACKs. The default behavior is unchanged; however, the limit can be activated by changing the new net.inet.tcp.rack.split_limit sysctl. Submitted by: Peter Lei <peterlei@netflix.com> Reported by: jtl Reviewed by: lstewart (earlier version) Security: CVE-2019-5599
This commit is contained in:
Jonathan T. Looney
parent
eeea0fcf0f
commit
5e02b277a4
Notes:
svn2git
2020-12-20 02:59:44 +00:00
svn path=/head/; revision=349192
@ -1,5 +1,5 @@
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/*-
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* Copyright (c) 2016-2018 Netflix, Inc.
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* Copyright (c) 2016-2019 Netflix, Inc.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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@ -202,6 +202,7 @@ static int32_t rack_always_send_oldest = 0;
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static int32_t rack_sack_block_limit = 128;
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static int32_t rack_use_sack_filter = 1;
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static int32_t rack_tlp_threshold_use = TLP_USE_TWO_ONE;
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static uint32_t rack_map_split_limit = 0; /* unlimited by default */
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/* Rack specific counters */
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counter_u64_t rack_badfr;
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@ -227,6 +228,8 @@ counter_u64_t rack_to_arm_tlp;
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counter_u64_t rack_to_alloc;
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counter_u64_t rack_to_alloc_hard;
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counter_u64_t rack_to_alloc_emerg;
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counter_u64_t rack_alloc_limited_conns;
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counter_u64_t rack_split_limited;
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counter_u64_t rack_sack_proc_all;
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counter_u64_t rack_sack_proc_short;
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@ -260,6 +263,8 @@ static void
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rack_ack_received(struct tcpcb *tp, struct tcp_rack *rack,
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struct tcphdr *th, uint16_t nsegs, uint16_t type, int32_t recovery);
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static struct rack_sendmap *rack_alloc(struct tcp_rack *rack);
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static struct rack_sendmap *rack_alloc_limit(struct tcp_rack *rack,
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uint8_t limit_type);
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static struct rack_sendmap *
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rack_check_recovery_mode(struct tcpcb *tp,
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uint32_t tsused);
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@ -444,6 +449,8 @@ sysctl_rack_clear(SYSCTL_HANDLER_ARGS)
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counter_u64_zero(rack_sack_proc_short);
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counter_u64_zero(rack_sack_proc_restart);
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counter_u64_zero(rack_to_alloc);
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counter_u64_zero(rack_alloc_limited_conns);
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counter_u64_zero(rack_split_limited);
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counter_u64_zero(rack_find_high);
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counter_u64_zero(rack_runt_sacks);
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counter_u64_zero(rack_used_tlpmethod);
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@ -621,6 +628,11 @@ rack_init_sysctls()
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OID_AUTO, "pktdelay", CTLFLAG_RW,
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&rack_pkt_delay, 1,
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"Extra RACK time (in ms) besides reordering thresh");
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SYSCTL_ADD_U32(&rack_sysctl_ctx,
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SYSCTL_CHILDREN(rack_sysctl_root),
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OID_AUTO, "split_limit", CTLFLAG_RW,
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&rack_map_split_limit, 0,
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"Is there a limit on the number of map split entries (0=unlimited)");
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SYSCTL_ADD_S32(&rack_sysctl_ctx,
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SYSCTL_CHILDREN(rack_sysctl_root),
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OID_AUTO, "inc_var", CTLFLAG_RW,
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@ -756,7 +768,19 @@ rack_init_sysctls()
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SYSCTL_CHILDREN(rack_sysctl_root),
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OID_AUTO, "allocemerg", CTLFLAG_RD,
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&rack_to_alloc_emerg,
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"Total alocations done from emergency cache");
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"Total allocations done from emergency cache");
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rack_alloc_limited_conns = counter_u64_alloc(M_WAITOK);
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SYSCTL_ADD_COUNTER_U64(&rack_sysctl_ctx,
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SYSCTL_CHILDREN(rack_sysctl_root),
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OID_AUTO, "alloc_limited_conns", CTLFLAG_RD,
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&rack_alloc_limited_conns,
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"Connections with allocations dropped due to limit");
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rack_split_limited = counter_u64_alloc(M_WAITOK);
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SYSCTL_ADD_COUNTER_U64(&rack_sysctl_ctx,
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SYSCTL_CHILDREN(rack_sysctl_root),
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OID_AUTO, "split_limited", CTLFLAG_RD,
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&rack_split_limited,
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"Split allocations dropped due to limit");
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rack_sack_proc_all = counter_u64_alloc(M_WAITOK);
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SYSCTL_ADD_COUNTER_U64(&rack_sysctl_ctx,
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SYSCTL_CHILDREN(rack_sysctl_root),
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@ -1120,10 +1144,11 @@ rack_alloc(struct tcp_rack *rack)
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{
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struct rack_sendmap *rsm;
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counter_u64_add(rack_to_alloc, 1);
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rack->r_ctl.rc_num_maps_alloced++;
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rsm = uma_zalloc(rack_zone, M_NOWAIT);
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if (rsm) {
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alloc_done:
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counter_u64_add(rack_to_alloc, 1);
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rack->r_ctl.rc_num_maps_alloced++;
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return (rsm);
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}
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if (rack->rc_free_cnt) {
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@ -1131,14 +1156,46 @@ rack_alloc(struct tcp_rack *rack)
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rsm = TAILQ_FIRST(&rack->r_ctl.rc_free);
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TAILQ_REMOVE(&rack->r_ctl.rc_free, rsm, r_next);
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rack->rc_free_cnt--;
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return (rsm);
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goto alloc_done;
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}
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return (NULL);
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}
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/* wrapper to allocate a sendmap entry, subject to a specific limit */
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static struct rack_sendmap *
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rack_alloc_limit(struct tcp_rack *rack, uint8_t limit_type)
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{
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struct rack_sendmap *rsm;
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if (limit_type) {
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/* currently there is only one limit type */
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if (rack_map_split_limit > 0 &&
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rack->r_ctl.rc_num_split_allocs >= rack_map_split_limit) {
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counter_u64_add(rack_split_limited, 1);
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if (!rack->alloc_limit_reported) {
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rack->alloc_limit_reported = 1;
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counter_u64_add(rack_alloc_limited_conns, 1);
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}
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return (NULL);
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}
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}
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/* allocate and mark in the limit type, if set */
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rsm = rack_alloc(rack);
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if (rsm != NULL && limit_type) {
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rsm->r_limit_type = limit_type;
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rack->r_ctl.rc_num_split_allocs++;
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}
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return (rsm);
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}
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static void
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rack_free(struct tcp_rack *rack, struct rack_sendmap *rsm)
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{
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if (rsm->r_limit_type) {
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/* currently there is only one limit type */
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rack->r_ctl.rc_num_split_allocs--;
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}
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rack->r_ctl.rc_num_maps_alloced--;
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if (rack->r_ctl.rc_tlpsend == rsm)
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rack->r_ctl.rc_tlpsend = NULL;
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@ -3953,7 +4010,7 @@ rack_proc_sack_blk(struct tcpcb *tp, struct tcp_rack *rack, struct sackblk *sack
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/*
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* Need to split this in two pieces the before and after.
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*/
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nrsm = rack_alloc(rack);
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nrsm = rack_alloc_limit(rack, RACK_LIMIT_TYPE_SPLIT);
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if (nrsm == NULL) {
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/*
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* failed XXXrrs what can we do but loose the sack
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@ -4014,7 +4071,7 @@ rack_proc_sack_blk(struct tcpcb *tp, struct tcp_rack *rack, struct sackblk *sack
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goto do_rest_ofb;
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}
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/* Ok we need to split off this one at the tail */
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nrsm = rack_alloc(rack);
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nrsm = rack_alloc_limit(rack, RACK_LIMIT_TYPE_SPLIT);
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if (nrsm == NULL) {
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/* failed rrs what can we do but loose the sack info? */
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goto out;
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@ -54,8 +54,10 @@ struct rack_sendmap {
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uint8_t r_sndcnt; /* Retran count, not limited by
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* RACK_NUM_OF_RETRANS */
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uint8_t r_in_tmap; /* Flag to see if its in the r_tnext array */
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uint8_t r_resv[3];
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uint8_t r_limit_type; /* is this entry counted against a limit? */
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uint8_t r_resv[2];
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};
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#define RACK_LIMIT_TYPE_SPLIT 1
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TAILQ_HEAD(rack_head, rack_sendmap);
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@ -241,7 +243,7 @@ struct rack_control {
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uint32_t rc_num_maps_alloced; /* Number of map blocks (sacks) we
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* have allocated */
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uint32_t rc_rcvtime; /* When we last received data */
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uint32_t rc_notused;
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uint32_t rc_num_split_allocs; /* num split map entries allocated */
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uint32_t rc_last_output_to;
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uint32_t rc_went_idle_time;
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@ -310,7 +312,8 @@ struct tcp_rack {
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uint8_t rack_tlp_threshold_use;
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uint8_t rc_allow_data_af_clo: 1,
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delayed_ack : 1,
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rc_avail : 6;
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alloc_limit_reported : 1,
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rc_avail : 5;
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uint8_t r_resv[2]; /* Fill to cache line boundary */
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/* Cache line 2 0x40 */
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struct rack_control r_ctl;
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