sx_maxsockbuf.c

#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>

#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#include "sx_report.h"

#ifndef SX_MAXSOCKBUF_MAX
#define SX_MAXSOCKBUF_MAX (2*1024*1024)
#endif

int
sx_maxsockbuf(int s, int dir)
{ 
	int optval=0, voptval;
	int hiconf=-1, loconf=-1;
	unsigned int voptlen;
	int phase=0, iterations=0;

	if(s<0) { 
		sx_report(SX_FATAL,"Unable to maximize sockbuf on invalid socket %i\n",
			s);
		exit(1);
	};


	voptlen=sizeof(optval);
	if(getsockopt(s,SOL_SOCKET,dir,(void*)&optval,&voptlen)==-1) {
		sx_report(SX_ERROR,"initial getsockopt failed: %s\n", strerror(errno));
		return -1;
	};

	for(;;) { 
		iterations++;
		if(phase==0) optval<<=1; 
		else { 
			if(optval==(hiconf+loconf)/2) break;
			optval=(hiconf+loconf)/2;
		};
		if(optval>SX_MAXSOCKBUF_MAX && phase==0) 
			break;

		if(setsockopt(s,SOL_SOCKET,dir,(void*)&optval,sizeof(optval))==-1)
		{
			if(phase==0) phase=1; 
			hiconf=optval; 
			continue;
		} else { 
			loconf=optval;
		};

		voptlen=sizeof(voptval);

		if(getsockopt(s,SOL_SOCKET,dir,(void*)&voptval,&voptlen)==-1) {
			sx_report(SX_ERROR,"getsockopt failed: %s\n", strerror(errno));
			return -1;
		} else if(voptval<optval) { 
			if(phase==0) { 
				phase=1; optval>>=1; continue;
			} else if(phase==1) { 
				phase=2; optval-=2048; continue;
			} else break;
		} else if(voptval>=SX_MAXSOCKBUF_MAX) { 
			/* ... and getsockopt not failed and voptval>=optval. Do not allow
			 * to increase sockbuf too much even in case OS permits it */
			break;
		};
	};


	voptlen=sizeof(voptval);
	if(getsockopt(s,SOL_SOCKET,dir,(void*)&voptval,&voptlen)==-1) {
		sx_report(SX_ERROR,"getsockopt(final stage) failed: %s\n", 
			strerror(errno));
		return -1;
	} else { 
		/*
		printf("Finally got %i bytes of recvspace in %i interations\n", 
			voptval, iterations);
		*/
	};
	return voptval;
};