[PATCH libnetfilter_queue 07/32] src: Convert nfq_set_verdict() and nfq_set_verdict2() to use libmnl if there is no data

[Duncan Roe <duncan_roe@optusnet.com.au>]

static __set_verdict() uses mnl-API calls in enough places that the path
for no (mangled) data doesn't use any nfnl-API functions.
With no data, __set_verdict() uses sendto() (faster than sendmsg()).
nfq_set_verdict2() must not use htonl() on the packet mark.
checkpatch Block comments warning is fixed in a later commit.

Signed-off-by: Duncan Roe <duncan_roe@optusnet.com.au>
---
 src/libnetfilter_queue.c | 35 ++++++++++++++++-------------------
 1 file changed, 16 insertions(+), 19 deletions(-)

diff --git a/src/libnetfilter_queue.c b/src/libnetfilter_queue.c
index 58875b1..17fe879 100644
--- a/src/libnetfilter_queue.c
+++ b/src/libnetfilter_queue.c
@@ -38,8 +38,8 @@
 /* so won't try to validate higher-numbered attrs but will store them. */
 /* mnl API programs will then be able to access them. */
 #include <linux/netfilter/nfnetlink.h>
+#include <linux/netfilter/nfnetlink_compat.h>
 
-#include <libnfnetlink/libnfnetlink.h>
 #include <libnetfilter_queue/libnetfilter_queue.h>
 #include "internal.h"
 
@@ -912,13 +912,8 @@ static int __set_verdict(struct nfq_q_handle *qh, uint32_t id,
 		uint32_t data_len, const unsigned char *data,
 		enum nfqnl_msg_types type)
 {
-	struct nfqnl_msg_verdict_hdr vh;
-	union {
-		char buf[NFNL_HEADER_LEN
-			+NFA_LENGTH(sizeof(mark))
-			+NFA_LENGTH(sizeof(vh))];
-		struct nlmsghdr nmh;
-	} u;
+	char buf[MNL_SOCKET_BUFFER_SIZE];
+	struct nlmsghdr *nlh;
 
 	struct iovec iov[3];
 	int nvecs;
@@ -929,20 +924,22 @@ static int __set_verdict(struct nfq_q_handle *qh, uint32_t id,
 
 	memset(iov, 0, sizeof(iov));
 
-	vh.verdict = htonl(verdict);
-	vh.id = htonl(id);
-
-	nfnl_fill_hdr(qh->h->nfnlssh, &u.nmh, 0, AF_UNSPEC, qh->id,
-				type, NLM_F_REQUEST);
+	nlh = nfq_nlmsg_put(buf, NFQNL_MSG_VERDICT, qh->id);
 
 	/* add verdict header */
-	nfnl_addattr_l(&u.nmh, sizeof(u), NFQA_VERDICT_HDR, &vh, sizeof(vh));
+	nfq_nlmsg_verdict_put(nlh, id, verdict);
 
 	if (set_mark)
-		nfnl_addattr32(&u.nmh, sizeof(u), NFQA_MARK, mark);
+		nfq_nlmsg_verdict_put_mark(nlh, mark);
+
+	/* Efficiency gain: when there is only 1 iov,
+	 * sendto() is faster than sendmsg() because the kernel only has
+	 * 1 userspace address to validate instead of 2. */
+	if (!data_len)
+		return mnl_socket_sendto(qh->h->nl, nlh, nlh->nlmsg_len);
 
-	iov[0].iov_base = &u.nmh;
-	iov[0].iov_len = NLMSG_TAIL(&u.nmh) - (void *)&u.nmh;
+	iov[0].iov_base = nlh;
+	iov[0].iov_len = NLMSG_TAIL(nlh) - (void *)nlh;
 	nvecs = 1;
 
 	if (data_len) {
@@ -956,7 +953,7 @@ static int __set_verdict(struct nfq_q_handle *qh, uint32_t id,
 		 * header.  The size of the attribute is given in the
 		 * nla_len field and is set in the nfnl_build_nfa_iovec()
 		 * function. */
-		u.nmh.nlmsg_len += data_attr.nla_len;
+		nlh->nlmsg_len += data_attr.nla_len;
 	}
 
 	return nfnl_sendiov(qh->h->nfnlh, iov, nvecs, 0);
@@ -1013,7 +1010,7 @@ int nfq_set_verdict2(struct nfq_q_handle *qh, uint32_t id,
 		     uint32_t verdict, uint32_t mark,
 		     uint32_t data_len, const unsigned char *buf)
 {
-	return __set_verdict(qh, id, verdict, htonl(mark), 1, data_len,
+	return __set_verdict(qh, id, verdict, mark, 1, data_len,
 						buf, NFQNL_MSG_VERDICT);
 }
 
-- 
2.35.8