[Qemu-devel] [PATCH 1/6] linux-user: convert /proc/net/route when endianess differs

[Laurent Vivier <laurent@vivier.eu>]

This patch allows to have IP addresses in correct order
in the case of "netstat -nr" when the endianess of the
guest differs from one of the host.

For instance, an m68k guest on an x86_64 host:

WITHOUT this patch:

$ netstat -nr
Kernel IP routing table
Destination     Gateway         Genmask         Flags   MSS Window  irtt Iface
0.0.0.0         1.3.0.10        0.0.0.0         UG        0 0          0 eth0
0.3.0.10        0.0.0.0         0.255.255.255   U         0 0          0 eth0
$ cat /proc/net/route
Iface	Destination	Gateway 	Flags	RefCnt	Use	Metric	Mask	MTU	Window	IRTT

eth0	00000000	0103000A	0003	0	0	0	000000000	0	0
eth0	0003000A	00000000	0001	0	0	0	00FFFFFF0	0	0

WITH this patch:

$ netstat -nr
Kernel IP routing table
Destination     Gateway         Genmask         Flags   MSS Window  irtt Iface
0.0.0.0         10.0.3.1        0.0.0.0         UG        0 0          0 eth0
10.0.3.0        0.0.0.0         255.255.255.0   U         0 0          0 eth0
$ cat /proc/net/route
Iface	Destination	Gateway 	Flags	RefCnt	Use	Metric	Mask	MTU	Window	IRTT
eth0	00000000	0a000301	0003	0	0	0	000000000	0	0
eth0	0a000300	00000000	0001	0	0	0	ffffff000	0	0

Signed-off-by: Laurent Vivier <laurent@vivier.eu>
---
 linux-user/syscall.c | 58 +++++++++++++++++++++++++++++++++++++++++++++++-----
 1 file changed, 53 insertions(+), 5 deletions(-)

diff --git a/linux-user/syscall.c b/linux-user/syscall.c
index f986548..b19f712 100644
--- a/linux-user/syscall.c
+++ b/linux-user/syscall.c
@@ -5037,22 +5037,70 @@ static int is_proc_myself(const char *filename, const char *entry)
     return 0;
 }
 
+#if defined(HOST_WORDS_BIGENDIAN) != defined(TARGET_WORDS_BIGENDIAN)
+static int is_proc(const char *filename, const char *entry)
+{
+    return strcmp(filename, entry) == 0;
+}
+
+static int open_net_route(void *cpu_env, int fd)
+{
+    FILE *fp;
+    char *line = NULL;
+    size_t len = 0;
+    ssize_t read;
+
+    fp = fopen("/proc/net/route", "r");
+    if (fp == NULL) {
+        return -EACCES;
+    }
+
+    /* read header */
+
+    read = getline(&line, &len, fp);
+    dprintf(fd, "%s", line);
+
+    /* read routes */
+
+    while ((read = getline(&line, &len, fp)) != -1) {
+        char iface[16];
+        uint32_t dest, gw, mask;
+        unsigned int flags, refcnt, use, metric, mtu, window, irtt;
+        sscanf(line, "%s\t%08x\t%08x\t%04x\t%d\t%d\t%d\t%08x\t%d\t%u\t%u\n",
+                     iface, &dest, &gw, &flags, &refcnt, &use, &metric,
+                     &mask, &mtu, &window, &irtt);
+        dprintf(fd, "%s\t%08x\t%08x\t%04x\t%d\t%d\t%d\t%08x\t%d\t%u\t%u\n",
+                iface, tswap32(dest), tswap32(gw), flags, refcnt, use,
+                metric, tswap32(mask), mtu, window, irtt);
+    }
+
+    free(line);
+    fclose(fp);
+
+    return 0;
+}
+#endif
+
 static int do_open(void *cpu_env, const char *pathname, int flags, mode_t mode)
 {
     struct fake_open {
         const char *filename;
         int (*fill)(void *cpu_env, int fd);
+        int (*cmp)(const char *s1, const char *s2);
     };
     const struct fake_open *fake_open;
     static const struct fake_open fakes[] = {
-        { "maps", open_self_maps },
-        { "stat", open_self_stat },
-        { "auxv", open_self_auxv },
-        { NULL, NULL }
+        { "maps", open_self_maps, is_proc_myself },
+        { "stat", open_self_stat, is_proc_myself },
+        { "auxv", open_self_auxv, is_proc_myself },
+#if defined(HOST_WORDS_BIGENDIAN) != defined(TARGET_WORDS_BIGENDIAN)
+        { "/proc/net/route", open_net_route, is_proc },
+#endif
+        { NULL, NULL, NULL }
     };
 
     for (fake_open = fakes; fake_open->filename; fake_open++) {
-        if (is_proc_myself(pathname, fake_open->filename)) {
+        if (fake_open->cmp(pathname, fake_open->filename)) {
             break;
         }
     }
-- 
1.8.1.2