From 6cbe512525bf95cd04e7416f865c4a225d092490 Mon Sep 17 00:00:00 2001
From: Ralph Ronnquist <ralph.ronnquist@gmail.com>
Date: Thu, 10 Nov 2022 14:11:08 +1100
Subject: [PATCH] capturing for ipv4

---
 rrqnet.c | 60 +++++++++++++++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 57 insertions(+), 3 deletions(-)

diff --git a/rrqnet.c b/rrqnet.c
index 005fd20..cf0617e 100644
--- a/rrqnet.c
+++ b/rrqnet.c
@@ -26,6 +26,7 @@
 #include <sys/stat.h>
 #include <sys/time.h>
 #include <sys/types.h>
+#include <sys/socket.h>
 #include <time.h>
 #include <unistd.h>
 
@@ -64,7 +65,8 @@ struct Allowed {
 
 // Details of actualized connections.
 struct Remote {
-    struct SockAddr uaddr;
+    struct SockAddr uaddr;	// The remote IP address
+    struct SockAddr iaddr;	// The receiving IP address
     struct Allowed *spec;	// Rule being instantiated
     struct timeval rec_when;	// Last received packet time, in seconds
 };
@@ -83,6 +85,7 @@ typedef struct _PacketItem {
     QueueItem base;
     int fd;
     struct SockAddr src;
+    struct SockAddr dst;
     ssize_t len;
     unsigned char buffer[ BUFSIZE ];
 } PacketItem;
@@ -1256,6 +1259,46 @@ void todolist_initialize(int nbuf,int nthr) {
     }
 }
 
+static ssize_t recvpacket(int fd,PacketItem *p) {
+    int flags = udp6? IPV6_PKTINFO : IP_PKTINFO;
+    socklen_t addrlen =
+	udp6? sizeof( p->src.in6 ) : sizeof( p->src.in4 );
+    struct iovec buffer = {
+	.iov_base = p->buffer,
+	.iov_len = BUFSIZE
+    };
+    char data[1000];
+    struct msghdr msg = {
+	.msg_name =  &p->src.in,
+	.msg_namelen = addrlen,
+	.msg_iov = &buffer,
+	.msg_iovlen = 1,
+	.msg_control = data,
+	.msg_controllen = sizeof( data ),
+	.msg_flags = flags // Return value
+    };
+    p->len = recvmsg( fd, &msg, flags );
+    struct cmsghdr *cmsg = CMSG_FIRSTHDR( &msg );
+    VERBOSE3OUT( "anc %p %ld\n", cmsg, p->len );
+    for ( ; cmsg; cmsg = CMSG_NXTHDR( &msg, cmsg ) ) {
+	VERBOSE3OUT( "anc type = %d\n", cmsg->cmsg_type );
+    }
+    cmsg = CMSG_FIRSTHDR( &msg );
+    if ( cmsg ) {
+	if ( udp6 ) {
+	} else {
+	    struct in_pktinfo* pinf = (struct in_pktinfo*) CMSG_DATA( cmsg );
+	    p->dst.in4.sin_family = AF_INET;
+	    p->dst.in4.sin_addr = pinf->ipi_addr;
+	    VERBOSE3OUT( "DEST= %d %s\n",
+			 pinf->ipi_ifindex, inet_stoa( &p->dst ) );
+	}
+    }
+    return p->len;
+}
+
+
+
 // Read a full UDP packet into the given buffer, associate with a
 // connection, or create a new connection, the decrypt the as
 // specified, and capture the sender MAC address. The connection table
@@ -1266,18 +1309,24 @@ static void *doreadUDP(void *data) {
     int fd = ((ReaderData *) data)->fd;
     while ( 1 ) {
 	PacketItem *todo = (PacketItem *) Queue_getItem( &todolist.free );
+#if 0 
 	socklen_t addrlen =
 	    udp6? sizeof( todo->src.in6 ) : sizeof( todo->src.in4 );
+#endif
 	memset( &todo->src, 0, sizeof( todo->src ) );
 	todo->fd = fd;
+#if 0
 	todo->len = recvfrom(
 	    fd, todo->buffer, BUFSIZE, 0, &todo->src.in, &addrlen );
-	if ( todo->len == -1) {
+#endif
+	VERBOSE3OUT( "Reading packet\n" );
+	ssize_t len = recvpacket( fd, todo );
+	if ( len == -1) {
 	    perror( "Receiving UDP" );
 	    exit( 1 );
 	}
 #ifdef GPROF
-	if ( todo->len == 17 &&
+	if ( len == 17 &&
 	     memcmp( todo->buffer, "STOPSTOPSTOPSTOP", 16 ) == 0 ) {
 	    exit( 0 );
 	}
@@ -1612,6 +1661,11 @@ int main(int argc, char *argv[]) {
 	    exit(1);
 	}
 	VERBOSEOUT( "Using ipv4 UDP at %d\n", udp_fd );
+	int opt = 1;
+	if ( setsockopt( udp_fd, IPPROTO_IP, IP_PKTINFO, &opt, sizeof(opt)) ) {
+	    fprintf( stderr, "Error configuring socket!\n");
+            exit(1);
+	}
     } else {
 	// set up ipv6 socket
 	if ( ( udp_fd = socket( AF_INET6, SOCK_DGRAM, 0 ) ) == 0 ) {
-- 
2.39.2