From 0052078cf4cb03b23c49ef1cd65f69df746890b4 Mon Sep 17 00:00:00 2001 From: Florian Westphal Date: Fri, 26 Apr 2013 10:21:16 +0200 Subject: examples/nf-queue: handle recv error, use larger buffer We ask for 0xffff copy size, so we need a buffer that can hold 0xffff, plus a few more bytes to allow for netlink attributes. Also, turn off/handle ENOBUFS. Signed-off-by: Florian Westphal --- examples/nf-queue.c | 37 ++++++++++++++++++++++++------------- 1 file changed, 24 insertions(+), 13 deletions(-) diff --git a/examples/nf-queue.c b/examples/nf-queue.c index 7adac21..6641a24 100644 --- a/examples/nf-queue.c +++ b/examples/nf-queue.c @@ -1,3 +1,4 @@ +#include #include #include #include @@ -82,7 +83,9 @@ static int queue_cb(const struct nlmsghdr *nlh, void *data) int main(int argc, char *argv[]) { - char buf[MNL_SOCKET_BUFFER_SIZE]; + char *buf; + /* largest possible packet payload, plus netlink data overhead: */ + size_t sizeof_buf = 0xffff + (MNL_SOCKET_BUFFER_SIZE/2); struct nlmsghdr *nlh; int ret; unsigned int portid, queue_num; @@ -105,6 +108,12 @@ int main(int argc, char *argv[]) } portid = mnl_socket_get_portid(nl); + buf = malloc(sizeof_buf); + if (!buf) { + perror("allocate receive buffer"); + exit(EXIT_FAILURE); + } + nlh = nfq_hdr_put(buf, NFQNL_MSG_CONFIG, 0); nfq_nlmsg_cfg_put_cmd(nlh, AF_INET, NFQNL_CFG_CMD_PF_UNBIND); @@ -137,23 +146,25 @@ int main(int argc, char *argv[]) exit(EXIT_FAILURE); } - ret = mnl_socket_recvfrom(nl, buf, sizeof(buf)); - if (ret == -1) { - perror("mnl_socket_recvfrom"); - exit(EXIT_FAILURE); - } - while (ret > 0) { - ret = mnl_cb_run(buf, ret, 0, portid, queue_cb, NULL); - if (ret < 0){ - perror("mnl_cb_run"); - exit(EXIT_FAILURE); - } + /* ENOBUFS is signalled to userspace when packets were lost + * on kernel side. In most cases, userspace isn't interested + * in this information, so turn it off. + */ + ret = 1; + mnl_socket_setsockopt(nl, NETLINK_NO_ENOBUFS, &ret, sizeof(int)); - ret = mnl_socket_recvfrom(nl, buf, sizeof(buf)); + for (;;) { + ret = mnl_socket_recvfrom(nl, buf, sizeof_buf); if (ret == -1) { perror("mnl_socket_recvfrom"); exit(EXIT_FAILURE); } + + ret = mnl_cb_run(buf, ret, 0, portid, queue_cb, NULL); + if (ret < 0){ + perror("mnl_cb_run"); + exit(EXIT_FAILURE); + } } mnl_socket_close(nl); -- cgit v1.2.3