From 412c52e9ab9d5d1d1a1e5e09a122cca43895451a Mon Sep 17 00:00:00 2001 From: Phil Sutter Date: Mon, 5 Oct 2020 16:06:49 +0200 Subject: [PATCH] nft: Fix for concurrent noflush restore calls Transaction refresh was broken with regards to nft_chain_restore(): It created a rule flush batch object only if the chain was found in cache and a chain add object only if the chain was not found. Yet with concurrent ruleset updates, one has to expect both situations: * If a chain vanishes, the rule flush job must be skipped and instead the chain add job become active. * If a chain appears, the chain add job must be skipped and instead rules flushed. Change the code accordingly: Create both batch objects and set their 'skip' field depending on the situation in cache and adjust both in nft_refresh_transaction(). As a side-effect, the implicit rule flush becomes explicit and all handling of implicit batch jobs is dropped along with the related field indicating such. Reuse the 'implicit' parameter of __nft_rule_flush() to control the initial 'skip' field value instead. A subtle caveat is vanishing of existing chains: Creating the chain add job based on the chain in cache causes a netlink message containing that chain's handle which the kernel dislikes. Therefore unset the chain's handle in that case. Fixes: 58d7de0181f61 ("xtables: handle concurrent ruleset modifications") Signed-off-by: Phil Sutter (cherry picked from commit dac904bdcd9a18aabafee7275ccf0c2bd53800f3) --- iptables/nft.c | 58 ++++++++++--------- .../ipt-restore/0016-concurrent-restores_0 | 53 +++++++++++++++++ 2 files changed, 83 insertions(+), 28 deletions(-) create mode 100755 iptables/tests/shell/testcases/ipt-restore/0016-concurrent-restores_0 diff --git a/iptables/nft.c b/iptables/nft.c index d3eb0840a9fc0..bdb633a82a655 100644 --- a/iptables/nft.c +++ b/iptables/nft.c @@ -265,7 +265,6 @@ struct obj_update { struct list_head head; enum obj_update_type type:8; uint8_t skip:1; - uint8_t implicit:1; unsigned int seq; union { struct nftnl_table *table; @@ -1668,7 +1667,7 @@ struct nftnl_set *nft_set_batch_lookup_byid(struct nft_handle *h, static void __nft_rule_flush(struct nft_handle *h, const char *table, - const char *chain, bool verbose, bool implicit) + const char *chain, bool verbose, bool skip) { struct obj_update *obj; struct nftnl_rule *r; @@ -1690,7 +1689,7 @@ __nft_rule_flush(struct nft_handle *h, const char *table, return; } - obj->implicit = implicit; + obj->skip = skip; } int nft_rule_flush(struct nft_handle *h, const char *chain, const char *table, @@ -1786,17 +1785,12 @@ int nft_chain_user_add(struct nft_handle *h, const char *chain, const char *tabl int nft_chain_restore(struct nft_handle *h, const char *chain, const char *table) { struct nftnl_chain_list *list; + struct obj_update *obj; struct nftnl_chain *c; bool created = false; c = nft_chain_find(h, table, chain); - if (c) { - /* Apparently -n still flushes existing user defined - * chains that are redefined. - */ - if (h->noflush) - __nft_rule_flush(h, table, chain, false, true); - } else { + if (!c) { c = nftnl_chain_alloc(); if (!c) return 0; @@ -1804,20 +1798,26 @@ int nft_chain_restore(struct nft_handle *h, const char *chain, const char *table nftnl_chain_set_str(c, NFTNL_CHAIN_TABLE, table); nftnl_chain_set_str(c, NFTNL_CHAIN_NAME, chain); created = true; - } - if (h->family == NFPROTO_BRIDGE) - nftnl_chain_set_u32(c, NFTNL_CHAIN_POLICY, NF_ACCEPT); + list = nft_chain_list_get(h, table, chain); + if (list) + nftnl_chain_list_add(c, list); + } else { + /* If the chain should vanish meanwhile, kernel genid changes + * and the transaction is refreshed enabling the chain add + * object. With the handle still set, kernel interprets it as a + * chain replace job and errors since it is not found anymore. + */ + nftnl_chain_unset(c, NFTNL_CHAIN_HANDLE); + } - if (!created) - return 1; + __nft_rule_flush(h, table, chain, false, created); - if (!batch_chain_add(h, NFT_COMPAT_CHAIN_USER_ADD, c)) + obj = batch_chain_add(h, NFT_COMPAT_CHAIN_USER_ADD, c); + if (!obj) return 0; - list = nft_chain_list_get(h, table, chain); - if (list) - nftnl_chain_list_add(c, list); + obj->skip = !created; /* the core expects 1 for success and 0 for error */ return 1; @@ -2751,11 +2751,6 @@ static void nft_refresh_transaction(struct nft_handle *h) h->error.lineno = 0; list_for_each_entry_safe(n, tmp, &h->obj_list, head) { - if (n->implicit) { - batch_obj_del(h, n); - continue; - } - switch (n->type) { case NFT_COMPAT_TABLE_FLUSH: tablename = nftnl_table_get_str(n->table, NFTNL_TABLE_NAME); @@ -2781,14 +2776,22 @@ static void nft_refresh_transaction(struct nft_handle *h) c = nft_chain_find(h, tablename, chainname); if (c) { - /* -restore -n flushes existing rules from redefined user-chain */ - __nft_rule_flush(h, tablename, - chainname, false, true); n->skip = 1; } else if (!c) { n->skip = 0; } break; + case NFT_COMPAT_RULE_FLUSH: + tablename = nftnl_rule_get_str(n->rule, NFTNL_RULE_TABLE); + if (!tablename) + continue; + + chainname = nftnl_rule_get_str(n->rule, NFTNL_RULE_CHAIN); + if (!chainname) + continue; + + n->skip = !nft_chain_find(h, tablename, chainname); + break; case NFT_COMPAT_TABLE_ADD: case NFT_COMPAT_CHAIN_ADD: case NFT_COMPAT_CHAIN_ZERO: @@ -2800,7 +2803,6 @@ static void nft_refresh_transaction(struct nft_handle *h) case NFT_COMPAT_RULE_INSERT: case NFT_COMPAT_RULE_REPLACE: case NFT_COMPAT_RULE_DELETE: - case NFT_COMPAT_RULE_FLUSH: case NFT_COMPAT_SET_ADD: case NFT_COMPAT_RULE_LIST: case NFT_COMPAT_RULE_CHECK: diff --git a/iptables/tests/shell/testcases/ipt-restore/0016-concurrent-restores_0 b/iptables/tests/shell/testcases/ipt-restore/0016-concurrent-restores_0 new file mode 100755 index 0000000000000..53ec12fa368af --- /dev/null +++ b/iptables/tests/shell/testcases/ipt-restore/0016-concurrent-restores_0 @@ -0,0 +1,53 @@ +#!/bin/bash + +set -e + +RS="*filter +:INPUT ACCEPT [12024:3123388] +:FORWARD ACCEPT [0:0] +:OUTPUT ACCEPT [12840:2144421] +:FOO - [0:0] +:BAR0 - [0:0] +:BAR1 - [0:0] +:BAR2 - [0:0] +:BAR3 - [0:0] +:BAR4 - [0:0] +:BAR5 - [0:0] +:BAR6 - [0:0] +:BAR7 - [0:0] +:BAR8 - [0:0] +:BAR9 - [0:0] +" + +RS1="$RS +-X BAR3 +-X BAR6 +-X BAR9 +-A FOO -s 9.9.0.1/32 -j BAR1 +-A FOO -s 9.9.0.2/32 -j BAR2 +-A FOO -s 9.9.0.4/32 -j BAR4 +-A FOO -s 9.9.0.5/32 -j BAR5 +-A FOO -s 9.9.0.7/32 -j BAR7 +-A FOO -s 9.9.0.8/32 -j BAR8 +COMMIT +" + +RS2="$RS +-X BAR2 +-X BAR5 +-X BAR7 +-A FOO -s 9.9.0.1/32 -j BAR1 +-A FOO -s 9.9.0.3/32 -j BAR3 +-A FOO -s 9.9.0.4/32 -j BAR4 +-A FOO -s 9.9.0.6/32 -j BAR6 +-A FOO -s 9.9.0.8/32 -j BAR8 +-A FOO -s 9.9.0.9/32 -j BAR9 +COMMIT +" + +for n in $(seq 1 10); do + $XT_MULTI iptables-restore --noflush -w <<< "$RS1" & + $XT_MULTI iptables-restore --noflush -w <<< "$RS2" & + wait -n + wait -n +done -- 2.40.0