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-rw-r--r--examples/nf-queue.c66
1 files changed, 51 insertions, 15 deletions
diff --git a/examples/nf-queue.c b/examples/nf-queue.c
index 7adac21..1f465ad 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>
@@ -50,7 +51,7 @@ static int queue_cb(const struct nlmsghdr *nlh, void *data)
{
struct nfqnl_msg_packet_hdr *ph = NULL;
struct nlattr *attr[NFQA_MAX+1] = {};
- uint32_t id = 0;
+ uint32_t id = 0, skbinfo;
struct nfgenmsg *nfg;
uint16_t plen;
@@ -71,10 +72,32 @@ static int queue_cb(const struct nlmsghdr *nlh, void *data)
plen = mnl_attr_get_payload_len(attr[NFQA_PAYLOAD]);
/* void *payload = mnl_attr_get_payload(attr[NFQA_PAYLOAD]); */
+ skbinfo = attr[NFQA_SKB_INFO] ? ntohl(mnl_attr_get_u32(attr[NFQA_SKB_INFO])) : 0;
+
+ if (attr[NFQA_CAP_LEN]) {
+ uint32_t orig_len = ntohl(mnl_attr_get_u32(attr[NFQA_CAP_LEN]));
+ if (orig_len != plen)
+ printf("truncated ");
+ }
+
+ if (skbinfo & NFQA_SKB_GSO)
+ printf("GSO ");
+
id = ntohl(ph->packet_id);
- printf("packet received (id=%u hw=0x%04x hook=%u, payload len %u)\n",
+ printf("packet received (id=%u hw=0x%04x hook=%u, payload len %u",
id, ntohs(ph->hw_protocol), ph->hook, plen);
+ /*
+ * ip/tcp checksums are not yet valid, e.g. due to GRO/GSO.
+ * The application should behave as if the checksums are correct.
+ *
+ * If these packets are later forwarded/sent out, the checksums will
+ * be corrected by kernel/hardware.
+ */
+ if (skbinfo & NFQA_SKB_CSUMNOTREADY)
+ printf(", checksum not ready");
+ puts(")");
+
nfq_send_verdict(ntohs(nfg->res_id), id);
return MNL_CB_OK;
@@ -82,7 +105,9 @@ 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 +130,12 @@ 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);
@@ -132,28 +163,33 @@ int main(int argc, char *argv[])
nlh = nfq_hdr_put(buf, NFQNL_MSG_CONFIG, queue_num);
nfq_nlmsg_cfg_put_params(nlh, NFQNL_COPY_PACKET, 0xffff);
+ mnl_attr_put_u32(nlh, NFQA_CFG_FLAGS, htonl(NFQA_CFG_F_GSO));
+ mnl_attr_put_u32(nlh, NFQA_CFG_MASK, htonl(NFQA_CFG_F_GSO));
+
if (mnl_socket_sendto(nl, nlh, nlh->nlmsg_len) < 0) {
perror("mnl_socket_send");
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);