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-rw-r--r--examples/nf-queue.c66
-rw-r--r--include/libnetfilter_queue/linux_nfnetlink_queue.h13
-rw-r--r--include/linux/netfilter/nfnetlink_queue.h21
-rw-r--r--src/libnetfilter_queue.c17
-rw-r--r--src/nlmsg.c2
5 files changed, 98 insertions, 21 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);
diff --git a/include/libnetfilter_queue/linux_nfnetlink_queue.h b/include/libnetfilter_queue/linux_nfnetlink_queue.h
index 58c8ca5..81a485b 100644
--- a/include/libnetfilter_queue/linux_nfnetlink_queue.h
+++ b/include/libnetfilter_queue/linux_nfnetlink_queue.h
@@ -45,6 +45,10 @@ enum nfqnl_attr_type {
NFQA_IFINDEX_PHYSOUTDEV, /* u_int32_t ifindex */
NFQA_HWADDR, /* nfqnl_msg_packet_hw */
NFQA_PAYLOAD, /* opaque data payload */
+ NFQA_CT, /* nf_conntrack_netlink.h */
+ NFQA_CT_INFO, /* enum ip_conntrack_info */
+ NFQA_CAP_LEN, /* __u32 length of captured packet */
+ NFQA_SKB_INFO, /* __u32 skb meta information */
__NFQA_MAX
};
@@ -96,6 +100,13 @@ enum nfqnl_attr_config {
/* Flags/options for NFQA_CFG_FLAGS */
#define NFQA_CFG_F_FAIL_OPEN (1 << 0)
#define NFQA_CFG_F_CONNTRACK (1 << 1)
-#define NFQA_CFG_F_MAX (1 << 2)
+#define NFQA_CFG_F_GSO (1 << 2)
+#define NFQA_CFG_F_MAX (1 << 3)
+
+/* flags for NFQA_SKB_INFO */
+/* packet appears to have wrong checksums, but they are ok */
+#define NFQA_SKB_CSUMNOTREADY (1 << 0)
+/* packet is GSO (i.e., exceeds device mtu) */
+#define NFQA_SKB_GSO (1 << 1)
#endif /* _NFNETLINK_QUEUE_H */
diff --git a/include/linux/netfilter/nfnetlink_queue.h b/include/linux/netfilter/nfnetlink_queue.h
index da44b33..a2308ae 100644
--- a/include/linux/netfilter/nfnetlink_queue.h
+++ b/include/linux/netfilter/nfnetlink_queue.h
@@ -44,6 +44,8 @@ enum nfqnl_attr_type {
NFQA_PAYLOAD, /* opaque data payload */
NFQA_CT, /* nf_conntrack_netlink.h */
NFQA_CT_INFO, /* enum ip_conntrack_info */
+ NFQA_CAP_LEN, /* __u32 length of captured packet */
+ NFQA_SKB_INFO, /* __u32 skb meta information */
__NFQA_MAX
};
@@ -80,19 +82,28 @@ struct nfqnl_msg_config_params {
__u8 copy_mode; /* enum nfqnl_config_mode */
} __attribute__ ((packed));
-enum nfqnl_flags {
- NFQNL_F_NONE = 0,
- NFQNL_F_CONNTRACK = (1 << 0),
-};
enum nfqnl_attr_config {
NFQA_CFG_UNSPEC,
NFQA_CFG_CMD, /* nfqnl_msg_config_cmd */
NFQA_CFG_PARAMS, /* nfqnl_msg_config_params */
NFQA_CFG_QUEUE_MAXLEN, /* __u32 */
- NFQA_CFG_FLAGS, /* __u32 */
+ NFQA_CFG_MASK, /* identify which flags to change */
+ NFQA_CFG_FLAGS, /* value of these flags (__u32) */
__NFQA_CFG_MAX
};
#define NFQA_CFG_MAX (__NFQA_CFG_MAX-1)
+/* Flags for NFQA_CFG_FLAGS */
+#define NFQA_CFG_F_FAIL_OPEN (1 << 0)
+#define NFQA_CFG_F_CONNTRACK (1 << 1)
+#define NFQA_CFG_F_GSO (1 << 2)
+#define NFQA_CFG_F_MAX (1 << 3)
+
+/* flags for NFQA_SKB_INFO */
+/* packet appears to have wrong checksums, but they are ok */
+#define NFQA_SKB_CSUMNOTREADY (1 << 0)
+/* packet is GSO (i.e., exceeds device mtu) */
+#define NFQA_SKB_GSO (1 << 1)
+
#endif /* _NFNETLINK_QUEUE_H */
diff --git a/src/libnetfilter_queue.c b/src/libnetfilter_queue.c
index bf944f0..6817957 100644
--- a/src/libnetfilter_queue.c
+++ b/src/libnetfilter_queue.c
@@ -640,6 +640,23 @@ int nfq_set_mode(struct nfq_q_handle *qh,
* - NFQA_CFG_F_CONNTRACK (requires Linux kernel >= 3.6): the kernel will
* include the Connection Tracking system information.
*
+ * - NFQA_CFG_F_GSO (requires Linux kernel >= 3.10): the kernel will
+ * not normalize offload packets, i.e. your application will need to
+ * be able to handle packets larger than the mtu (up to 64k).
+ *
+ * If your application validates checksums (e.g., tcp checksum),
+ * then you must also check if the NFQA_SKB_INFO attribute is present.
+ * If it is, you need to test the NFQA_SKB_CSUMNOTREADY bit:
+ * \verbatim
+ if (attr[NFQA_SKB_INFO]) {
+ uint32_t info = ntohl(mnl_attr_get_u32(attr[NFQA_SKB_INFO]));
+ if (info & NFQA_SKB_CSUMNOTREADY)
+ validate_checksums = false;
+ }
+\endverbatim
+ * if this bit is set, the layer 3/4 checksums of the packet appear incorrect,
+ * but are not (because they will be corrected later by the kernel).
+ *
* Here's a little code snippet to show how to use this API:
* \verbatim
uint32_t flags = NFQA_CFG_F_FAIL_OPEN;
diff --git a/src/nlmsg.c b/src/nlmsg.c
index 6c4a139..e7a30e0 100644
--- a/src/nlmsg.c
+++ b/src/nlmsg.c
@@ -132,6 +132,8 @@ static int nfq_pkt_parse_attr_cb(const struct nlattr *attr, void *data)
case NFQA_IFINDEX_OUTDEV:
case NFQA_IFINDEX_PHYSINDEV:
case NFQA_IFINDEX_PHYSOUTDEV:
+ case NFQA_CAP_LEN:
+ case NFQA_SKB_INFO:
if (mnl_attr_validate(attr, MNL_TYPE_U32) < 0)
return MNL_CB_ERROR;
break;