Hi, After this patch was applied I have not been able to enable tethering. Through debugging I found that function __connman_nat_enable returns the error: "Cannot enable NAT -9/Bad file descriptor", this error is gotten when parameter ip_forward is trying to be modified by editing the file with write() fucntion. Trying to find the reason of the error I added the O_RDWR mode in open() to check if it was a permissions problem but it did not work and it continue giving the same error. Next, I tried to come back to fopen() instead of use open() and it worked. What do you think is happening? What is wrong when file "/proc/sys/net/ipv4/ip_forward" is handled with the system calls open/read/write instead of standard functions fopen/fprintf/fscanf? Best regards, Jose Blanquicet -----Original Message----- From: connman [mailto:connman-bounces@lists.01.org] On Behalf Of Patrik Flykt Sent: martedì 12 aprile 2016 15:02 To: connman(a)lists.01.org Subject: [PATCH v2] nat: Remember previous IPv4 forwarding value When NAT is enabled, store the previous IPv4 forwarding setting so that it can be restored to its former value when disabling NAT. --- v2: Fix err = -errno and fix a few conditionals to be more readable src/nat.c | 40 ++++++++++++++++++++++++++++++---------- 1 file changed, 30 insertions(+), 10 deletions(-) diff --git a/src/nat.c b/src/nat.c index 063f085..b739e11 100644 --- a/src/nat.c +++ b/src/nat.c @@ -25,7 +25,10 @@ #endif #include <errno.h> -#include <stdio.h> +#include <sys/types.h> +#include <sys/stat.h> +#include <fcntl.h> +#include <unistd.h> #include "connman.h" @@ -42,20 +45,37 @@ struct connman_nat { static int enable_ip_forward(bool enable) { - FILE *f; + static char value = 0; + int f, err = 0; - f = fopen("/proc/sys/net/ipv4/ip_forward", "r+"); - if (!f) + if ((f = open("/proc/sys/net/ipv4/ip_forward", O_CLOEXEC)) < 0) return -errno; - if (enable) - fprintf(f, "1"); - else - fprintf(f, "0"); + if (!value) { + if (read(f, &value, sizeof(value)) < 0) + value = 0; + } - fclose(f); + if (enable) { + char allow = '1'; - return 0; + if (write (f, &allow, sizeof(allow)) < 0) + err = -errno; + } else { + char deny = '0'; + + if (value) + deny = value; + + if (write(f, &deny, sizeof(deny)) < 0) + err = -errno; + + value = 0; + } + + close(f); + + return err; } static int enable_nat(struct connman_nat *nat) -- 2.8.0.rc3 _______________________________________________ connman mailing list connman(a)lists.01.org https://lists.01.org/mailman/listinfo/connman