Running ADSserver fails with SEGFAULT

[Ronny Schröder]

Hi,

I compiled the libads package downloaded from github.
When I try to run the ADSserver from examples folder the binary crashes immediately after startup:

See the log running ADSserver with gdb:
> Starting program: /.../libads-master/examples/.libs/ADSserver 48898
> [Thread debugging using libthread_db enabled]
>
> Breakpoint 1, ADSGetLocalAMSId (id=0x804b228) at ads.c:833
> 833 {
> (gdb) n
> 839 if (getifaddrs(&list) < 0) {
> (gdb)
> 844 for (cur = list; cur != NULL; cur = cur->ifa_next) {
> (gdb)
> 846 && (strcmp(cur->ifa_name, "lo") != 0)) {
> (gdb)
> 844 for (cur = list; cur != NULL; cur = cur->ifa_next) {
> (gdb)
> 845 if ((cur->ifa_addr->sa_family == AF_INET)
> (gdb)
> 857 if (cur->ifa_next == NULL)
> (gdb)
> 844 for (cur = list; cur != NULL; cur = cur->ifa_next) {
> (gdb)
> 845 if ((cur->ifa_addr->sa_family == AF_INET)
> (gdb)
> 857 if (cur->ifa_next == NULL)
> (gdb)
> 844 for (cur = list; cur != NULL; cur = cur->ifa_next) {
> (gdb)
> 845 if ((cur->ifa_addr->sa_family == AF_INET)
> (gdb)
> 857 if (cur->ifa_next == NULL)
> (gdb)
> 844 for (cur = list; cur != NULL; cur = cur->ifa_next) {
> (gdb)
> 845 if ((cur->ifa_addr->sa_family == AF_INET)
> (gdb)
>
> Program received signal SIGSEGV, Segmentation fault.
> 0x0012f8ab in ADSGetLocalAMSId (id=0x804b228) at ads.c:845
> 845 if ((cur->ifa_addr->sa_family == AF_INET)

System: Reelbox (generic x86 linux PC running ubuntu)

Any ideas what I am doing wrong here?

BR Ronny

[Håkon Nessjøen]

Do a check that:

cur->ifa_addr != NULL before checking cur->ifa_addr->sa_family == AF_INET

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[Luis Matos]

I'll add that check in the code!

Thanks!

Do a check that:

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[Luis Matos]

can it be like this:
diff --git a/src/ads.c b/src/ads.c
index 2f0e1a1..3a14e3c 100755
@@ -842,6 +842,9 @@ int ADSGetLocalAMSId(AMSNetID * id)
 
     struct ifaddrs *cur;

     for (cur = list; cur != NULL; cur = cur->ifa_next) {

+        if (cur->ifa_addr == NULL) {
+            break;
+        }

         if ((cur->ifa_addr->sa_family == AF_INET)

             && (strcmp(cur->ifa_name, "lo") != 0)) {

             addrStruct = (struct sockaddr_in *)cur->ifa_addr;

if ifa_addr is null, it means that it is an ethernet link that is down, right?

Cheers,
Luis Matos

[Ronny Schroeder]

Hi Luis,

Am Donnerstag, 7. März 2013 17:53:05 UTC+1 schrieb Luis Matos:

can it be like this:
diff --git a/src/ads.c b/src/ads.c
index 2f0e1a1..3a14e3c 100755
@@ -842,6 +842,9 @@ int ADSGetLocalAMSId(AMSNetID * id)
 
     struct ifaddrs *cur;
     for (cur = list; cur != NULL; cur = cur->ifa_next) {
+        if (cur->ifa_addr == NULL) {
+            break;
+        }
         if ((cur->ifa_addr->sa_family == AF_INET)
             && (strcmp(cur->ifa_name, "lo") != 0)) {
             addrStruct = (struct sockaddr_in *)cur->ifa_addr;

Great this fix works fine.

 

if ifa_addr is null, it means that it is an ethernet link that is down, right?

No idea, but in my case it was this tun device:

tun0      Link encap:UNSPEC  HWaddr 00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00  

          inet addr:192.168.99.130  P-t-P:192.168.99.130  Mask:255.255.255.252

          UP POINTOPOINT RUNNING NOARP MULTICAST  MTU:8300  Metric:1

          RX packets:1057 errors:0 dropped:0 overruns:0 frame:0

          TX packets:1056 errors:0 dropped:0 overruns:0 carrier:0

          collisions:0 txqueuelen:500 

          RX bytes:33847 (33.8 KB)  TX bytes:574017 (574.0 KB)

BR Ronny

[Håkon Nessjøen]

You should not "break" it, but "continue;"

If you break, it will not find any more interfaces after the first interface without an address.

Håkon

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[Luis Matos]

True ... my bad.
Uploaded.

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[Luis Matos]

humm ... thinking again ...
The correct way to handle this just check first for if_addr being NULL and later for the AF_NET.
Because, if this is the last network device, then, all would be messed anyway.

please check:
https://github.com/gass/libads/commit/f7febfe2a0171a18db793c00e080a207ee495420

[Håkon Nessjøen]

Yes, this is how i originally wanted you to do it :)

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[Håkon Nessjøen]

I have sent you a pull request, and added some code in my own repo, which you can pull if you want.

https://github.com/haakonnessjoen/libads/

On 8 March 2013 00:54, Luis Matos <ga...@otiliamatos.ath.cx> wrote:

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Håkon

[Luis Matos]

Hello,

Thank you for your contribution.

I've commented there that the only thing i disagree is the new dump function you created.

The ads dump function should changed to accomodate the number of items to dump.

cheers,

Luis Matos

[Håkon Nessjøen]

The ads dump function only work when adsdebug is on. So the example doesn't show anything if debug is not on. So I copied out the dump function from ads.c and removed the if expression.

I agree that it should be changed to only dump what is needed to dump.

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