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mptcpize: set GODEBUG=multipathtcp=1 env var #316

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mptcpize: set GODEBUG=multipathtcp=1 env var #316

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1074277
mptcpize: do not override existing LD_PRELOAD value
matttbe Nov 21, 2024
ee77b9c
mptcpize: set GODEBUG=multipathtcp=1 env var
matttbe Nov 21, 2024
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43 changes: 35 additions & 8 deletions src/mptcpize.c
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Original file line number Diff line number Diff line change
Expand Up @@ -34,7 +34,9 @@
#define SYSTEMD_SERVICE_TAG "[Service]"
#define SYSTEMCTL_SHOW "systemctl show -p FragmentPath "
#define PRELOAD_VAR "LD_PRELOAD="
#define MPTCPWRAP_ENV "LD_PRELOAD="PKGLIBDIR"/libmptcpwrap.so.0.0."LIBREVISION
#define MPTCPWRAP_ENV PKGLIBDIR"/libmptcpwrap.so.0.0."LIBREVISION
#define GODEBUG_VAR "GODEBUG="
#define MPTCPGO_ENV "multipathtcp=1"

/* Program documentation. */
static char args_doc[] = "CMD";
Expand Down Expand Up @@ -62,8 +64,9 @@ static void help(void)

static int run(int argc, char *av[])
{
int i, nr = 0, debug = 0;
char **envp, **argv;
int i, nr = 0, ld, go, debug = 0;
char **envp, **argv, *env;
size_t len;

if (argc > 0 && strcmp(av[0], "-d") == 0) {
debug = 1;
Expand All @@ -80,24 +83,48 @@ static int run(int argc, char *av[])
// build environment, copying the current one ...
while (environ[nr])
nr++;
envp = calloc(nr + 3, sizeof(char *));
envp = calloc(nr + 4, sizeof(char *));
if (!envp)
error(1, errno, "can't allocate env list");

// ... filtering out any 'LD_PRELOAD' ...
// ... filtering out any 'LD_PRELOAD' and 'GODEBUG' ...
nr = 0;
i = 0;
ld = -1;
go = -1;
while (environ[nr]) {
if (strncmp(environ[nr], PRELOAD_VAR,
strlen(PRELOAD_VAR)) != 0) {
strlen(PRELOAD_VAR)) == 0) {
ld = nr;
} else if (strncmp(environ[nr], GODEBUG_VAR,
strlen(GODEBUG_VAR)) == 0) {
go = nr;
} else {
envp[i] = environ[nr];
i++;
}
nr++;
}

// ... appending the mptcpwrap preload...
envp[i++] = MPTCPWRAP_ENV;
if (ld >= 0) {
len = strlen(environ[ld]) + strlen(MPTCPWRAP_ENV) + 2;
env = alloca(len);
snprintf(env, len, "%s:%s", environ[ld], MPTCPWRAP_ENV);
} else {
env = PRELOAD_VAR MPTCPWRAP_ENV;
}
envp[i++] = env;

// .. and GODEBUG=multipathtcp=1 ...
if (go >= 0) {
len = strlen(environ[go]) + strlen(MPTCPGO_ENV) + 2;
env = alloca(len);
snprintf(env, len, "%s,%s", environ[go], MPTCPGO_ENV);
} else {
env = GODEBUG_VAR MPTCPGO_ENV;
}
envp[i++] = env;

// ... and enable dbg if needed
if (debug)
Expand Down Expand Up @@ -204,7 +231,7 @@ static int unit_update(int argc, char *argv[], int enable)

if (append_env &&
(is_env || strncmp(line, SYSTEMD_SERVICE_TAG, strlen(SYSTEMD_SERVICE_TAG)) == 0)) {
if (dprintf(dst, "%s%s\n", SYSTEMD_ENV_VAR, MPTCPWRAP_ENV) < 0)
if (dprintf(dst, "%s%s\n", SYSTEMD_ENV_VAR, PRELOAD_VAR MPTCPWRAP_ENV) < 0)
error(1, errno, "can't write to env string into %s", dst_path);
append_env = 0;
}
Expand Down