On Fri, 24 May 2024 18:18:53 +0530 Danish Prakash <contact(a)danishpraka.sh> wrote:When invoking pasta without any arguments, it's difficult to tell whether we are in the new namespace or not leaving users a bit confused. This change modifies the host namespace to add a prefix "pasta-" to make it a bit more obvious. Signed-off-by: Danish Prakash <contact(a)danishpraka.sh> --- pasta.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/pasta.c b/pasta.c index 31e1e00..90afd74 100644 --- a/pasta.c +++ b/pasta.c @@ -50,6 +50,8 @@ #include "netlink.h" #include "log.h" +#define HOSTNAME_PREFIX "pasta-" + /* PID of child, in case we created a namespace */ int pasta_child_pid; @@ -178,6 +180,7 @@ struct pasta_spawn_cmd_arg { */ static int pasta_spawn_cmd(void *arg) { + char hostname[HOST_NAME_MAX + 1] = HOSTNAME_PREFIX; const struct pasta_spawn_cmd_arg *a; sigset_t set; @@ -188,6 +191,12 @@ static int pasta_spawn_cmd(void *arg) if (write_file("/proc/sys/net/ipv4/ping_group_range", "0 0")) warn("Cannot set ping_group_range, ICMP requests might fail"); + if (!gethostname(hostname + sizeof(HOSTNAME_PREFIX) - 1, HOST_NAME_MAX + 1 - sizeof(HOSTNAME_PREFIX)) ||Following the Linux kernel coding style also means we try to stick into 80 columns where possible: https://www.kernel.org/doc/html/latest/process/coding-style.html#breaking-l… ...so there was a reason why I proposed this line like I did, with the line splits. These subtleties, I can also fix them up on merge.+ errno == ENAMETOOLONG ) {Excess whitespace between ENAMETOOLONG and ). Same here, I would fix this up on merge.+ if (sethostname(hostname, strlen(hostname)))So, I mentioned before that you don't really need to set a NULL terminating byte for sethostname() itself, because it takes a length. But strlen() needs it. If gethostname() truncated the hostname, according to POSIX, it's unspecified whether we'll have a NULL byte at the end of 'hostname', and strlen() would read out-of-bounds, past the end of 'hostname'. That's not an issue with glibc, but if POSIX says it's not guaranteed, we shouldn't take anything for granted. I would suggest that you simply add a NULL byte at HOST_NAME_MAX, unconditionally, that should cover the normal case as well as the ENAMETOOLONG case. I haven't tested this by the way.+ warn("Unable to set pasta-prefixed hostname"); + } + /* Wait for the parent to be ready: see main() */ sigemptyset(&set); sigaddset(&set, SIGUSR1);-- Stefano