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Improve the sshnodelay hack after osxfuse's merge 

Document the strage-looking symbol interposition that is necessary for the
OS X case.

While doing this, homogenize the code to do the real connect call for both
the Linux and OS X cases into a helper function.  This logic is generic
and should not be replicated into various OS-specific cases.
This commit is contained in:
Julio Merino 2016-02-08 21:40:30 -05:00
parent 27e7029148
commit 80db43d7dc
1 changed files with 27 additions and 14 deletions
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41
sshnodelay.c
View File

@ -5,8 +5,32 @@
#include <netinet/in.h>
#include <netinet/tcp.h>
/* Wrapper around connect(2) to explicitly set TCP_NODELAY. */
static int nodelay_connect(
int (*real_connect)(int, const struct sockaddr *, socklen_t),
int sock, const struct sockaddr *addr, socklen_t addrlen)
{
int res = real_connect(sock, addr, addrlen);
if (!res && addr->sa_family == AF_INET) {
int opt = 1;
setsockopt(sock, IPPROTO_TCP, TCP_NODELAY, &opt, sizeof(opt));
}
return res;
}
#if __APPLE__
/* OS X does not have LD_PRELOAD but has DYLD_INSERT_LIBRARIES. The right
* environment variable is set by sshfs.c when attempting to load the
* sshnodelay workaround.
*
* However, things are not that simple: DYLD_INSERT_LIBRARIES does not
* behave exactly like LD_PRELOAD. Instead, the dyld dynamic linker will
* look for __DATA __interpose sections on the libraries given via the
* DYLD_INSERT_LIBRARIES variable. The contents of this section are pairs
* of replacement functions and functions to be replaced, respectively.
* Prepare such section here. */
int custom_connect(int sock, const struct sockaddr *addr, socklen_t addrlen);
typedef struct interpose_s {
@ -21,26 +45,15 @@ static const interpose_t interposers[] \
int custom_connect(int sock, const struct sockaddr *addr, socklen_t addrlen)
{
int res = connect(sock, addr, addrlen);
if (!res && addr->sa_family == AF_INET) {
int opt = 1;
setsockopt(sock, IPPROTO_TCP, TCP_NODELAY, &opt, sizeof(opt));
}
return res;
return nodelay_connect(connect, sock, addr, addrlen);
}
#else /* !__APPLE__ */
int connect(int sock, const struct sockaddr *addr, socklen_t addrlen)
{
int (*next_connect)(int, const struct sockaddr *, socklen_t) =
dlsym(RTLD_NEXT, "connect");
int res = next_connect(sock, addr, addrlen);
if (!res && addr->sa_family == AF_INET) {
int opt = 1;
setsockopt(sock, IPPROTO_TCP, TCP_NODELAY, &opt, sizeof(opt));
}
return res;
return nodelay_connect(dlsym(RTLD_NEXT, "connect"),
sock, addr, addrlen);
}
#endif /* !__APPLE__ */