From d05e9515b84074b0a0a49a2b49da31bd057bad7b Mon Sep 17 00:00:00 2001 From: Eyal Birger Date: Fri, 1 Jan 2021 11:02:26 +0200 Subject: examples: check return value of nfct_nlmsg_build() nfct_nlmsg_build() may fail for different reasons, for example if insufficient parameters exist in the ct object. The resulting nlh would not contain any of the ct attributes. Some conntrack operations would still operate in such case, for example an IPCTNL_MSG_CT_DELETE message would just delete all existing conntrack entries. While the example as it is does supply correct parameters, it's safer as reference to validate the return value. Signed-off-by: Eyal Birger Signed-off-by: Pablo Neira Ayuso --- examples/nfct-mnl-create.c | 6 +++++- examples/nfct-mnl-del.c | 6 +++++- examples/nfct-mnl-get.c | 6 +++++- examples/nfct-mnl-set-label.c | 7 ++++++- 4 files changed, 21 insertions(+), 4 deletions(-) diff --git a/examples/nfct-mnl-create.c b/examples/nfct-mnl-create.c index 64387a7..7fd224d 100644 --- a/examples/nfct-mnl-create.c +++ b/examples/nfct-mnl-create.c @@ -60,7 +60,11 @@ int main(void) nfct_set_attr_u8(ct, ATTR_TCP_STATE, TCP_CONNTRACK_SYN_SENT); nfct_set_attr_u32(ct, ATTR_TIMEOUT, 100); - nfct_nlmsg_build(nlh, ct); + ret = nfct_nlmsg_build(nlh, ct); + if (ret == -1) { + perror("nfct_nlmsg_build"); + exit(EXIT_FAILURE); + } ret = mnl_socket_sendto(nl, nlh, nlh->nlmsg_len); if (ret == -1) { diff --git a/examples/nfct-mnl-del.c b/examples/nfct-mnl-del.c index 91ad9e4..806d9f8 100644 --- a/examples/nfct-mnl-del.c +++ b/examples/nfct-mnl-del.c @@ -55,7 +55,11 @@ int main(void) nfct_set_attr_u16(ct, ATTR_PORT_SRC, htons(20)); nfct_set_attr_u16(ct, ATTR_PORT_DST, htons(10)); - nfct_nlmsg_build(nlh, ct); + ret = nfct_nlmsg_build(nlh, ct); + if (ret == -1) { + perror("nfct_nlmsg_build"); + exit(EXIT_FAILURE); + } ret = mnl_socket_sendto(nl, nlh, nlh->nlmsg_len); if (ret == -1) { diff --git a/examples/nfct-mnl-get.c b/examples/nfct-mnl-get.c index 4858acf..5be3331 100644 --- a/examples/nfct-mnl-get.c +++ b/examples/nfct-mnl-get.c @@ -74,7 +74,11 @@ int main(void) nfct_set_attr_u16(ct, ATTR_PORT_SRC, htons(20)); nfct_set_attr_u16(ct, ATTR_PORT_DST, htons(10)); - nfct_nlmsg_build(nlh, ct); + ret = nfct_nlmsg_build(nlh, ct); + if (ret == -1) { + perror("nfct_nlmsg_build"); + exit(EXIT_FAILURE); + } ret = mnl_socket_sendto(nl, nlh, nlh->nlmsg_len); if (ret == -1) { diff --git a/examples/nfct-mnl-set-label.c b/examples/nfct-mnl-set-label.c index c52b267..50bebb0 100644 --- a/examples/nfct-mnl-set-label.c +++ b/examples/nfct-mnl-set-label.c @@ -19,6 +19,7 @@ static void set_label(struct nf_conntrack *ct, struct callback_args *cbargs) char buf[MNL_SOCKET_BUFFER_SIZE]; struct nlmsghdr *nlh; struct nfgenmsg *nfh; + int ret; if (b) { if (bit < 0) @@ -55,7 +56,11 @@ static void set_label(struct nf_conntrack *ct, struct callback_args *cbargs) nfh->version = NFNETLINK_V0; nfh->res_id = 0; - nfct_nlmsg_build(nlh, ct); + ret = nfct_nlmsg_build(nlh, ct); + if (ret == -1) { + perror("nfct_nlmsg_build"); + exit(EXIT_FAILURE); + } if (mnl_socket_sendto(cbargs->nl, nlh, nlh->nlmsg_len) < 0) perror("mnl_socket_sendto"); -- cgit v1.2.3