From e2b60d54ab2f580cb4aef5a01c7b36a02aee6cc6 Mon Sep 17 00:00:00 2001 From: Pablo Neira Ayuso Date: Tue, 22 Jul 2014 22:16:59 +0200 Subject: mnl: introduce NFT_NLMSG_MAXSIZE The NFT_NLMSG_MAXSIZE constant defines the maximum nf_tables netlink message. Currently, the largest is the set element message, which contains the NFTA_SET_ELEM_LIST_ELEMENTS attribute. This attribute is a nest that describes the set elements. Given that the netlink attribute length (nla_len) is 16 bits, the largest message is a bit larger than 64 KBytes. Thus, the proposed value of NFT_NLMSG_MAXSIZE is set to (1 << 16) + getpagesize(). This new constant is used to calculate the length of: 1) the batch page length, when the batching mode is used. 2) the buffer that stores the netlink message in the send (when no batching is used) and receive paths. Signed-off-by: Pablo Neira Ayuso --- src/mnl.c | 18 +++++++++++++----- 1 file changed, 13 insertions(+), 5 deletions(-) diff --git a/src/mnl.c b/src/mnl.c index 42b11f5b..667aa3a7 100644 --- a/src/mnl.c +++ b/src/mnl.c @@ -33,11 +33,19 @@ uint32_t mnl_seqnum_alloc(void) return seq++; } +/* The largest nf_tables netlink message is the set element message, which + * contains the NFTA_SET_ELEM_LIST_ELEMENTS attribute. This attribute is + * a nest that describes the set elements. Given that the netlink attribute + * length (nla_len) is 16 bits, the largest message is a bit larger than + * 64 KBytes. + */ +#define NFT_NLMSG_MAXSIZE (UINT16_MAX + getpagesize()) + static int nft_mnl_recv(struct mnl_socket *nf_sock, uint32_t seqnum, uint32_t portid, int (*cb)(const struct nlmsghdr *nlh, void *data), void *cb_data) { - char buf[MNL_SOCKET_BUFFER_SIZE]; + char buf[NFT_NLMSG_MAXSIZE]; int ret; ret = mnl_socket_recvfrom(nf_sock, buf, sizeof(buf)); @@ -86,8 +94,8 @@ static struct mnl_nlmsg_batch *mnl_batch_alloc(void) { static char *buf; - /* libmnl needs higher buffer to handle batch overflows */ - buf = xmalloc(BATCH_PAGE_SIZE + getpagesize()); + /* libmnl needs higher buffer to handle batch overflows. */ + buf = xmalloc(BATCH_PAGE_SIZE + NFT_NLMSG_MAXSIZE); return mnl_nlmsg_batch_start(buf, BATCH_PAGE_SIZE); } @@ -818,7 +826,7 @@ int mnl_nft_set_get(struct mnl_socket *nf_sock, struct nft_set *nls) int mnl_nft_setelem_add(struct mnl_socket *nf_sock, struct nft_set *nls, unsigned int flags) { - char buf[MNL_SOCKET_BUFFER_SIZE]; + char buf[NFT_NLMSG_MAXSIZE]; struct nlmsghdr *nlh; nlh = nft_set_elem_nlmsg_build_hdr(buf, NFT_MSG_NEWSETELEM, @@ -832,7 +840,7 @@ int mnl_nft_setelem_add(struct mnl_socket *nf_sock, struct nft_set *nls, int mnl_nft_setelem_delete(struct mnl_socket *nf_sock, struct nft_set *nls, unsigned int flags) { - char buf[MNL_SOCKET_BUFFER_SIZE]; + char buf[NFT_NLMSG_MAXSIZE]; struct nlmsghdr *nlh; nlh = nft_set_elem_nlmsg_build_hdr(buf, NFT_MSG_DELSETELEM, -- cgit v1.2.3