To avoid forwarding loops, we need to exclude certain ports from being
auto-forwarded. To accomplish this, procfs_scan_listen() takes a bitmap
of exclusions. As it detects each port, it checks against that bitmap.
This is a complicated way of accomplishing what we need. We can instead
mask out the excluded ports in the callers using a new bitmap_andc()
helper.
Signed-off-by: David Gibson
---
fwd.c | 32 ++++++++++++++------------------
util.c | 23 +++++++++++++++++++++++
util.h | 1 +
3 files changed, 38 insertions(+), 18 deletions(-)
diff --git a/fwd.c b/fwd.c
index 19309f14..c7b768d5 100644
--- a/fwd.c
+++ b/fwd.c
@@ -110,13 +110,11 @@ bool fwd_port_is_ephemeral(in_port_t port)
* @fd: fd for relevant /proc/net file
* @lstate: Code for listening state to scan for
* @map: Bitmap where numbers of ports in listening state will be set
- * @exclude: Bitmap of ports to exclude from setting (and clear)
*
* #syscalls:pasta lseek
* #syscalls:pasta ppc64le:_llseek ppc64:_llseek arm:_llseek
*/
-static void procfs_scan_listen(int fd, unsigned int lstate,
- uint8_t *map, const uint8_t *exclude)
+static void procfs_scan_listen(int fd, unsigned int lstate, uint8_t *map)
{
struct lineread lr;
unsigned long port;
@@ -141,10 +139,7 @@ static void procfs_scan_listen(int fd, unsigned int lstate,
if (state != lstate)
continue;
- if (bitmap_isset(exclude, port))
- bitmap_clear(map, port);
- else
- bitmap_set(map, port);
+ bitmap_set(map, port);
}
}
@@ -157,8 +152,9 @@ static void fwd_scan_ports_tcp(struct fwd_ports *fwd,
const struct fwd_ports *rev)
{
memset(fwd->map, 0, PORT_BITMAP_SIZE);
- procfs_scan_listen(fwd->scan4, TCP_LISTEN, fwd->map, rev->map);
- procfs_scan_listen(fwd->scan6, TCP_LISTEN, fwd->map, rev->map);
+ procfs_scan_listen(fwd->scan4, TCP_LISTEN, fwd->map);
+ procfs_scan_listen(fwd->scan6, TCP_LISTEN, fwd->map);
+ bitmap_andc(fwd->map, PORT_BITMAP_SIZE, fwd->map, rev->map);
}
/**
@@ -173,26 +169,26 @@ static void fwd_scan_ports_udp(struct fwd_ports *fwd,
const struct fwd_ports *tcp_fwd,
const struct fwd_ports *tcp_rev)
{
- uint8_t exclude[PORT_BITMAP_SIZE];
-
- bitmap_or(exclude, PORT_BITMAP_SIZE, rev->map, tcp_rev->map);
-
memset(fwd->map, 0, PORT_BITMAP_SIZE);
- procfs_scan_listen(fwd->scan4, UDP_LISTEN, fwd->map, exclude);
- procfs_scan_listen(fwd->scan6, UDP_LISTEN, fwd->map, exclude);
+ procfs_scan_listen(fwd->scan4, UDP_LISTEN, fwd->map);
+ procfs_scan_listen(fwd->scan6, UDP_LISTEN, fwd->map);
/* Also forward UDP ports with the same numbers as bound TCP ports.
* This is useful for a handful of protocols (e.g. iperf3) where a TCP
* control port is used to set up transfers on a corresponding UDP
* port.
- *
+ */
+ procfs_scan_listen(tcp_fwd->scan4, TCP_LISTEN, fwd->map);
+ procfs_scan_listen(tcp_fwd->scan6, TCP_LISTEN, fwd->map);
+
+ /*
* This means we need to skip numbers of TCP ports bound on the other
* side, too. Otherwise, we would detect corresponding UDP ports as
* bound and try to forward them from the opposite side, but it's
* already us handling them.
*/
- procfs_scan_listen(tcp_fwd->scan4, TCP_LISTEN, fwd->map, exclude);
- procfs_scan_listen(tcp_fwd->scan6, TCP_LISTEN, fwd->map, exclude);
+ bitmap_andc(fwd->map, PORT_BITMAP_SIZE, fwd->map, rev->map);
+ bitmap_andc(fwd->map, PORT_BITMAP_SIZE, fwd->map, tcp_rev->map);
}
/**
diff --git a/util.c b/util.c
index c492f904..eabadf7d 100644
--- a/util.c
+++ b/util.c
@@ -322,6 +322,7 @@ void bitmap_set(uint8_t *map, unsigned bit)
* @map: Pointer to bitmap
* @bit: Bit number to clear
*/
+/* cppcheck-suppress unusedFunction */
void bitmap_clear(uint8_t *map, unsigned bit)
{
unsigned long *word = (unsigned long *)map + BITMAP_WORD(bit);
@@ -351,6 +352,7 @@ bool bitmap_isset(const uint8_t *map, unsigned bit)
* @a: First operand
* @b: Second operand
*/
+/* cppcheck-suppress unusedFunction */
void bitmap_or(uint8_t *dst, size_t size, const uint8_t *a, const uint8_t *b)
{
unsigned long *dw = (unsigned long *)dst;
@@ -365,6 +367,27 @@ void bitmap_or(uint8_t *dst, size_t size, const uint8_t *a, const uint8_t *b)
dst[i] = a[i] | b[i];
}
+/**
+ * bitmap_andc() - Logical conjunction with complement (AND NOT) of bitmap
+ * @dst: Pointer to result bitmap
+ * @size: Size of bitmaps, in bytes
+ * @a: First operand
+ * @b: Second operand
+ */
+void bitmap_andc(uint8_t *dst, size_t size, const uint8_t *a, const uint8_t *b)
+{
+ unsigned long *dw = (unsigned long *)dst;
+ unsigned long *aw = (unsigned long *)a;
+ unsigned long *bw = (unsigned long *)b;
+ size_t i;
+
+ for (i = 0; i < size / sizeof(long); i++, dw++, aw++, bw++)
+ *dw = *aw & ~*bw;
+
+ for (i = size / sizeof(long) * sizeof(long); i < size; i++)
+ dst[i] = a[i] & ~b[i];
+}
+
/**
* ns_enter() - Enter configured user (unless already joined) and network ns
* @c: Execution context
diff --git a/util.h b/util.h
index 22eaac56..ac8339a3 100644
--- a/util.h
+++ b/util.h
@@ -213,6 +213,7 @@ void bitmap_set(uint8_t *map, unsigned bit);
void bitmap_clear(uint8_t *map, unsigned bit);
bool bitmap_isset(const uint8_t *map, unsigned bit);
void bitmap_or(uint8_t *dst, size_t size, const uint8_t *a, const uint8_t *b);
+void bitmap_andc(uint8_t *dst, size_t size, const uint8_t *a, const uint8_t *b);
char *line_read(char *buf, size_t len, int fd);
void ns_enter(const struct ctx *c);
bool ns_is_init(void);
--
2.51.0