| Message ID | 1366886611-21666-3-git-send-email-fw@strlen.de |
|---|---|
| State | Superseded |
| Headers | show |
On Thu, Apr 25, 2013 at 12:43:29PM +0200, Florian Westphal wrote: > 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 <fw@strlen.de> > --- > examples/nf-queue.c | 38 +++++++++++++++++++++++++------------- > 1 files changed, 25 insertions(+), 13 deletions(-) > > diff --git a/examples/nf-queue.c b/examples/nf-queue.c > index 7adac21..57ba483 100644 > --- a/examples/nf-queue.c > +++ b/examples/nf-queue.c > @@ -1,3 +1,4 @@ > +#include <errno.h> > #include <stdio.h> > #include <stdlib.h> > #include <unistd.h> > @@ -82,7 +83,8 @@ static int queue_cb(const struct nlmsghdr *nlh, void *data) > > int main(int argc, char *argv[]) > { > - char buf[MNL_SOCKET_BUFFER_SIZE]; > + char *buf; > + size_t sizeof_buf = 0xffff + 2084; I think users will appreciate a comment to explain why those black magic numbers are there ;-). Probably using MNL_SOCKET_BUFFER_SIZE/2 instead of 2084. > struct nlmsghdr *nlh; > int ret; > unsigned int portid, queue_num; > @@ -105,6 +107,12 @@ 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 +145,27 @@ 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) { > + if (errno == ENOBUFS) /* messages were lost */ Hm, you disabled ENOBUFS errors, right? > + continue; > 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); > -- > 1.7.8.6 > > -- > To unsubscribe from this list: send the line "unsubscribe netfilter-devel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe netfilter-devel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Pablo Neira Ayuso <pablo@netfilter.org> wrote: > On Thu, Apr 25, 2013 at 12:43:29PM +0200, Florian Westphal wrote: > > 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 <fw@strlen.de> > > --- > > examples/nf-queue.c | 38 +++++++++++++++++++++++++------------- > > 1 files changed, 25 insertions(+), 13 deletions(-) > > > > diff --git a/examples/nf-queue.c b/examples/nf-queue.c > > index 7adac21..57ba483 100644 > > --- a/examples/nf-queue.c > > +++ b/examples/nf-queue.c > > @@ -1,3 +1,4 @@ > > +#include <errno.h> > > #include <stdio.h> > > #include <stdlib.h> > > #include <unistd.h> > > @@ -82,7 +83,8 @@ static int queue_cb(const struct nlmsghdr *nlh, void *data) > > > > int main(int argc, char *argv[]) > > { > > - char buf[MNL_SOCKET_BUFFER_SIZE]; > > + char *buf; > > + size_t sizeof_buf = 0xffff + 2084; > > I think users will appreciate a comment to explain why those black > magic numbers are there ;-). Probably using MNL_SOCKET_BUFFER_SIZE/2 > instead of 2084. Good point :-) I'll do that and add a comment explaining this, e.g. "largest possible packet payload, plus netlink data overhead" > > + /* 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) { > > + if (errno == ENOBUFS) /* messages were lost */ > > Hm, you disabled ENOBUFS errors, right? True. I'll remove the check. -- To unsubscribe from this list: send the line "unsubscribe netfilter-devel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/examples/nf-queue.c b/examples/nf-queue.c index 7adac21..57ba483 100644 --- a/examples/nf-queue.c +++ b/examples/nf-queue.c @@ -1,3 +1,4 @@ +#include <errno.h> #include <stdio.h> #include <stdlib.h> #include <unistd.h> @@ -82,7 +83,8 @@ static int queue_cb(const struct nlmsghdr *nlh, void *data) int main(int argc, char *argv[]) { - char buf[MNL_SOCKET_BUFFER_SIZE]; + char *buf; + size_t sizeof_buf = 0xffff + 2084; struct nlmsghdr *nlh; int ret; unsigned int portid, queue_num; @@ -105,6 +107,12 @@ 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 +145,27 @@ 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) { + if (errno == ENOBUFS) /* messages were lost */ + continue; 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);
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 <fw@strlen.de> --- examples/nf-queue.c | 38 +++++++++++++++++++++++++------------- 1 files changed, 25 insertions(+), 13 deletions(-)