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net: nftables: avoid restore failure if the CRIU nft table already exist

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CRIU locks the network during restore in an "empty" network namespace.
However, "empty" in this context means CRIU isn't restoring the
namespace. This network namespace can be the same namespace where
processes have been dumped and so the network is already locked in it.

Fixes #2650

Signed-off-by: Andrei Vagin <avagin@gmail.com>
This commit is contained in:
Andrei Vagin 2025-04-21 06:33:41 +00:00 • committed by Andrei Vagin
parent b9da95b0b2
commit 5de61a721f
3 changed files with 19 additions and 15 deletions
Download patch file Download diff file Expand all files Collapse all files

2
criu/cr-restore.c
View file

@ -2119,7 +2119,7 @@ static int restore_root_task(struct pstree_item *init)
* the '--empty-ns net' mode no iptables C/R is done and we
* need to return these rules by hands.
*/
ret = network_lock_internal();
ret = network_lock_internal(/* restore = */ true);
if (ret)
goto out_kill;
}

2
criu/include/net.h
View file

@ -31,7 +31,7 @@ extern int collect_net_namespaces(bool for_dump);
extern int network_lock(void);
extern void network_unlock(void);
extern int network_lock_internal(void);
extern int network_lock_internal(bool restore);
extern struct ns_desc net_ns_desc;

30
criu/net.c
View file

@ -3206,12 +3206,12 @@ static inline FILE *redirect_nftables_output(struct nft_ctx *nft)
}
#endif
static inline int nftables_lock_network_internal(void)
static inline int nftables_lock_network_internal(bool restore)
{
#if defined(CONFIG_HAS_NFTABLES_LIB_API_0) || defined(CONFIG_HAS_NFTABLES_LIB_API_1)
cleanup_file FILE *fp = NULL;
struct nft_ctx *nft;
int ret = 0;
int ret = 0, exit_code = -1;
char table[32];
char buf[128];
@ -3224,11 +3224,16 @@ static inline int nftables_lock_network_internal(void)
fp = redirect_nftables_output(nft);
if (!fp)
goto out;
goto err2;
snprintf(buf, sizeof(buf), "create table %s", table);
if (NFT_RUN_CMD(nft, buf))
ret = NFT_RUN_CMD(nft, buf);
if (ret) {
/* The network has been locked on dump. */
if (restore && errno == EEXIST)
return 0;
goto err2;
}
snprintf(buf, sizeof(buf), "add chain %s output { type filter hook output priority 0; policy drop; }", table);
if (NFT_RUN_CMD(nft, buf))
@ -3246,17 +3251,16 @@ static inline int nftables_lock_network_internal(void)
if (NFT_RUN_CMD(nft, buf))
goto err1;
goto out;
exit_code = 0;
out:
nft_ctx_free(nft);
return exit_code;
err1:
snprintf(buf, sizeof(buf), "delete table %s", table);
NFT_RUN_CMD(nft, buf);
err2:
ret = -1;
pr_err("Locking network failed using nftables\n");
out:
nft_ctx_free(nft);
return ret;
goto out;
#else
pr_err("CRIU was built without libnftables support\n");
return -1;
@ -3288,7 +3292,7 @@ static int iptables_network_lock_internal(void)
return ret;
}
int network_lock_internal(void)
int network_lock_internal(bool restore)
{
int ret = 0, nsret;
@ -3301,7 +3305,7 @@ int network_lock_internal(void)
if (opts.network_lock_method == NETWORK_LOCK_IPTABLES)
ret = iptables_network_lock_internal();
else if (opts.network_lock_method == NETWORK_LOCK_NFTABLES)
ret = nftables_lock_network_internal();
ret = nftables_lock_network_internal(restore);
if (restore_ns(nsret, &net_ns_desc))
ret = -1;
@ -3427,7 +3431,7 @@ int network_lock(void)
if (run_scripts(ACT_NET_LOCK))
return -1;
return network_lock_internal();
return network_lock_internal(false);
}
void network_unlock(void)